Process and equipment for treating ammonium containing liquid

ABSTRACT

The process for treating an ammonium containing liquid by denitrification treatment of an ammonium containing liquid containing at least ammonium comprises carrying out nitrate reduction treatment of reducing nitrate contained in or added to the ammonium containing liquid to nitrite, and carrying out anaerobic ammonium oxidation treatment of simultaneously anaerobically denitrifying nitrite produced in the nitrate reduction treatment and ammonium contained in the ammonium containing liquid by anaerobic ammonium oxidizing bacteria.

This is a Division of application Ser. No. 11/359,529 filed Feb. 23,2006. The disclosure of the prior applications is hereby incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process and equipment for treating anammonium containing liquid, in particular, to a technology forbiologically denitrifying ammonium in an ammonium containing liquidgenerated in various fields such as the field of wastewater treatmentand the field of fine chemicals.

2. Description of the Related Art

Since the Mikawashima sewage treatment plant in Tokyo began operation offull-scale sewage treatment in 1922, sewage treatment plants haveoperated not only treatment of organic substances but also treatment ofnitrogen. In particular, governments of major cities have invested insewage treatment so that the sewerage coverage finally reached more than90%.

However, the sewerage has allowed almost no closed water areas to meetenvironmental standards. This is largely because of abnormal propagationof algae as an internal factor in water areas, but also because ofinflow wastewater as an external factor still to be eliminated. Inparticular, nitrogen is largely involved in the external factor.

Thus, a large amount is nitrogen is contained in sewage or wastewater inthe form of ammonium nitrogen. Ammonium containing liquids with low tohigh concentrations are generated in industrial wastewater, photographicdevelopment wastewater, and wastewater from chemical factories toproduce chemical products, for example. These ammonium containingliquids, if discharged as wastewater, cause eutrophication and loweringthe level of dissolved oxygen in waters, and thus it is necessary topurge ammonium before discharging the liquids. Further, it is necessaryto purge ammonium from liquid chemical products containing ammonium inorder to increase purity of the chemical products.

In these circumstances, ammonium containing liquids with lowconcentrations have been conventionally oxidized by chlorine orbiologically treated. In the chlorine treatment, chlorine is reactedwith ammonium to remove ammonium and produce chloramine at the sametime. The chlorine treatment is not used for treating ammoniumcontaining liquids with middle to high concentrations, since thechloramine is highly bactericidal and may disturb the ecosystem in theenvironment, and the treatment requires a large amount of chlorine. Suchliquids are typically biologically treated by nitrification anddenitrification.

The biological treatment by nitrification and denitrification isperformed in sewage treatment plants and wastewater treatment plants bynitrification in which ammonium is converted into nitrate throughnitrite by nitrifying bacteria, and denitrification in which nitrate isconverted into nitrogen gas by denitrifying bacteria. However, thetreatment of ammonium containing liquids by nitrification anddenitrification requires an organic substance in denitrificationreaction, and requires methanol to be added in an amount three timesgreater than nitrogen as the organic substance. In order to removenitrogen in a stable manner, such treatment must be operated at a lownitrogen load of 0.2 to 0.4 kg-N/m³/day. Accordingly, as theconcentration of ammonia is higher, a greater amount of expensivemethanol is used. Thus, a large tank is necessary as a treatment tank,and the treatment requires not only an initial cost but also a largerunning cost, disadvantageously.

In this situation, a process for treating wastewater utilizing anaerobicammonium oxidation has been attracted attention from a long time ago(for example, Japanese Patent Application Laid-Open No. 2001-037467).The anaerobic ammonium oxidation is a method comprising converting apart of ammonium to nitrite by nitrite-type nitrification reaction usingammonium oxidizing bacteria, with ammonium as an electron donor andnitrite as an electron acceptor, and simultaneously denitrifying thenitrite and the remaining ammonium using anaerobic ammonium oxidizingbacteria without requiring an organic substance. The anaerobic ammoniumoxidation requires only a small amount of oxygen in nitrificationreaction, does not require an organic substance (such as methanol) indenitrification reaction, and thus can be operated at a considerablyreduced running cost, advantageously. The anaerobic ammonium oxidationcan reduce the amount of sludge generated, for example, advantageously,and is assumed to be an effective wastewater treatment method in thefuture.

A large number of processes for treating ammonium containing liquids aswastewater by anaerobic ammonium oxidation disclosed in Japanese PatentApplication Laid-Open No. 2001-37467 have been proposed which areallegedly advantageous in significantly reducing the running cost.However, these processes have difficulty in practical use and have notbeen commonly employed.

This is because, in anaerobic ammonium oxidation, the reaction involvesnitrite as an electron acceptor but does not involve nitrate as anelectron acceptor, and thus nitrite must be supplied in a stable manner.

Specifically, when wastewater has a low ammonium nitrogen concentration,ammonium is easily oxidized to nitrate, and the amount of ammoniumoxidized to nitrite is necessarily small. Thus, the wastewater has aratio of ammonium to nitrite differing from such a ratio suitable foranaerobic ammonium oxidizing bacteria. In this manner, nitrificationreaction of converting a part of ammonium to nitrite is not stable, andthus the concentration of nitrite reacted with ammonium is easilychanged over time. Since it is thus difficult to react nitrite withammonium by denitrification constantly at a preferable ratio betweenthem, ammonium containing liquids cannot be treated in a stable manner,quality of the treated liquids tends to vary, and anaerobic ammoniumoxidation treatment cannot be efficiently carried out. In particular,wastewater such as sewage tends to have a low ammonium nitrogenconcentration, and it is thus difficult to treat such wastewater stablyfor a long time.

The present invention has been achieved in view of such circumstances.An object of the present invention is to provide a process and equipmentfor treating an ammonium containing liquid which can perform high-speeddenitrification of an ammonium containing liquid by anaerobic ammoniumoxidation or the like, without being affected by the change inconcentrations of nitrogen components in the ammonium containing liquidto be treated, and can provide a treated liquid with high qualityconstantly stably.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, to attain theaforementioned object, there is provided a process for treating anammonium containing liquid by denitrification treatment of an ammoniumcontaining liquid containing at least ammonium, the process comprisingcarrying out nitrate reduction treatment of reducing nitrate containedin or added to the ammonium containing liquid to nitrite, and carryingout anaerobic ammonium oxidation treatment of simultaneouslyanaerobically denitrifying nitrite produced in the nitrate reductiontreatment and ammonium contained in the ammonium containing liquid byanaerobic ammonium oxidizing bacteria.

According to the process for treating an ammonium containing liquid ofthe present invention, a conventional ammonium oxidation treatment ofcarrying out anaerobic ammonium oxidation treatment in which ammoniumand nitrite are simultaneously denitrified by anaerobic ammoniumoxidizing bacteria further comprises carrying out nitrate reductiontreatment of reducing nitrate forming a nitrogen component in anammonium containing liquid to nitrite. Consequently, even when anammonium containing liquid has low nitrite and ammonium concentrations,the nitrite concentration can be increased by reducing nitrate in theammonium containing liquid to nitrite by nitrate reduction treatment,and thus anaerobic ammonium oxidation treatment that allows high-speeddenitrification can be carried out in a stable manner. On the otherhand, even when an ammonium containing liquid has high ammonium andnitrite concentrations, nitrate contained in the ammonium containingliquid at a low concentration can be reduced to nitrite and, at the sametime, efficiently denitrified by anaerobic ammonium oxidation treatment.Accordingly, when the present invention is employed, an ammoniumcontaining liquid can be denitrified at a high speed in a stable mannerirrespective to the concentrations of nitrogen components contained inan ammonium containing liquid.

Here, nitrate added to an ammonium containing liquid is not limited tosynthetic nitrate added to the liquid, but includes nitrate obtained bybiologically nitrifying ammonium in ammonium wastewater using amicroorganism in a nitrification tank (aerobic tank). Hereinafter thesame.

According to a second aspect of the present invention, there is providedthe process for treating an ammonium containing liquid according to thefirst aspect, wherein the nitrate reduction treatment and the anaerobicammonium oxidation treatment are carried out by bringing the ammoniumcontaining liquid into contact with pellets in which heterotrophicdenitrifying bacteria that reduce the nitrate to nitrite using, as ahydrogen donor, an organic substance contained in or added to theammonium containing liquid are entrapped to be immobilized and pelletsin which the anaerobic ammonium oxidizing bacteria are entrapped to beimmobilized. According to a third aspect of the present invention, thereis provided the process for treating an ammonium containing liquidaccording to the first aspect, wherein the nitrate reduction treatmentand the anaerobic ammonium oxidation treatment are carried out bybringing the ammonium containing liquid into contact with pellets inwhich heterotrophic denitrifying bacteria that reduce the nitrate tonitrite using, as a hydrogen donor, an organic substance contained in oradded to the ammonium containing liquid and the anaerobic ammoniumoxidizing bacteria are entrapped to be immobilized.

According to the present invention, in the second aspect, an ammoniumcontaining liquid is brought into contact with pellets in whichheterotrophic denitrifying bacteria carrying out nitrate reductiontreatment are entrapped to be immobilized and pellets in which anaerobicammonium oxidizing bacteria are entrapped to be immobilized. In thethird aspect, an ammonium containing liquid is brought into contact withpellets in which both the heterotrophic denitrifying bacteria and theanaerobic ammonium oxidizing bacteria are entrapped to be immobilized.Thus, nitrate reduction treatment and anaerobic ammonium oxidationtreatment can be performed at the same time. Since heterotrophicdenitrifying bacteria and anaerobic ammonium oxidizing bacteria areentrapped to be immobilized in entrapping immobilization pellets easilyhandled, the contact rate of the bacteria with an ammonium containingliquid can be increased, and the growth rate of each bacteria in eachpellets and activity and operability of each treatment can be improved.Further, since the present invention can be applied to a conventionalanaerobic ammonium oxidation treatment process when the pellets in whichheterotrophic denitrifying bacteria are entrapped to be immobilizedaccording to the second aspect are employed in the process, or thepellets in which heterotrophic denitrifying bacteria and anaerobicammonium oxidizing bacteria are entrapped to be immobilized according tothe third aspect are employed instead of such pellets in the process.Therefore, such a process can be easily and inexpensively changed to thetreatment process of the present invention carrying out stablehigh-speed denitrification.

According to a fourth aspect of the present invention, there is providedthe process for treating an ammonium containing liquid according to thefirst aspect, wherein the nitrate reduction treatment and the anaerobicammonium oxidation treatment are carried out by bringing the ammoniumcontaining liquid into contact with pellets to which heterotrophicdenitrifying bacteria that reduce the nitrate to nitrite using, as ahydrogen donor, an organic substance contained in or added to theammonium containing liquid are attached to be immobilized and pellets towhich the anaerobic ammonium oxidizing bacteria are attached to beimmobilized. According to a fifth aspect of the present invention, thereis provided the process for treating an ammonium containing liquidaccording to the first aspect, wherein the nitrate reduction treatmentand the anaerobic ammonium oxidation treatment are carried out bybringing the ammonium containing liquid into contact with pellets towhich heterotrophic denitrifying bacteria that reduce the nitrate tonitrite using, as a hydrogen donor, an organic substance contained in oradded to the ammonium containing liquid and the anaerobic ammoniumoxidizing bacteria are attached to be immobilized.

The processes according to the fourth and fifth aspects can provide thesame effects as exhibited by the processes according to the second andthird aspects, and can reduce the labor and cost required forimmobilization of each bacteria as compared with entrappingimmobilization.

According to a sixth aspect of the present invention, there is providedthe process for treating an ammonium containing liquid according to thefirst aspect, wherein the nitrate reduction treatment is carried out bybringing the ammonium containing liquid into contact with a catalystthat reduces the nitrate as a nitrogen component to nitrite. In thenitrate reduction treatment of the present invention, the same effectscan be achieved by a chemical reaction using a catalyst. The catalyst ispreferably a Pd—Cu catalyst formed of an alloy of palladium and copper.Consequently, nitrate reduction treatment using a catalyst does notallow a metal to flow to treated water, and nitrate can be efficientlyreduced to nitrite.

According to an eighth aspect of the present invention, there isprovided the process for treating an ammonium containing liquidaccording to any one of the second to fifth aspects, wherein theheterotrophic denitrifying bacteria are controlled to have cells 10 to1,000 times of cells that the anaerobic ammonium oxidizing bacteriahave.

According to the present invention, since nitrate reduction treatmentand anaerobic ammonium oxidation treatment are carried out bycontrolling the ratio in number of cells of heterotrophic denitrifyingbacteria to anaerobic ammonium oxidizing bacteria to make these bacterialive symbiotically and coexist in a preferable state, the nitrogenremoval ratio can be improved.

According to a ninth aspect of the present invention, there is providedthe process for treating an ammonium containing liquid according to anyone of the first to eighth aspects, wherein the C/NO₃—N ratio of theconcentration C of the organic carbon contained in or added to theammonium containing liquid to the concentration NO₃—N of nitratenitrogen contained in or added to the ammonium containing liquid isdefined to be 0.5 to 2.5.

According to the present invention, efficiency in the aforementionednitrate reduction treatment and anaerobic ammonium oxidation treatmentis influenced by the ratio of the organic carbon concentration to thenitrate nitrogen concentration in an ammonium containing liquid to betreated. Specifically, when the C/NO₃—N ratio of the organic carbonconcentration C to the nitrate nitrogen concentration NO₃—N iscontrolled to be 0.5 to 2.5, heterotrophic denitrifying bacteria causeinsufficient nitrate reduction reaction, and thus nitrite in theammonium containing liquid to be treated can be easily accumulatedwithout being reduced to nitrogen gas. Consequently, accumulated nitriteand ammonium can be rapidly treated with anaerobic ammonium oxidizingbacteria, an ammonium containing liquid can be denitrified at a highspeed.

According to a tenth aspect of the present invention, to attain theaforementioned object, there is provided equipment for treating anammonium containing liquid by denitrification treatment of an ammoniumcontaining liquid containing at least ammonium, the equipment comprisinga nitrate reduction tank of reducing nitrate contained in or added tothe ammonium containing liquid to nitrite by heterotrophic denitrifyingbacteria using, as a hydrogen donor, an organic carbon contained in oradded to the ammonium containing liquid, and an anaerobic ammoniumoxidation tank of simultaneously anaerobically denitrifying nitriteproduced in the nitrate reduction tank and ammonium contained in theammonium containing liquid by anaerobic ammonium oxidizing bacteria.

The tenth aspect of the present invention shows a configuration ofequipment that implements the aforementioned processes for treating anammonium containing liquid according to the first to ninth aspects.

According to an eleventh aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to the tenth aspect, wherein the nitrate reduction tank has astructure of bringing the ammonium containing liquid into contact withpellets in which the heterotrophic denitrifying bacteria are entrappedto be immobilized, and the anaerobic ammonium oxidation tank has astructure of bringing the ammonium containing liquid treated in thenitrate reduction tank into contact with pellets in which the anaerobicammonium oxidizing bacteria are entrapped to be immobilized. Accordingto a twelfth aspect of the present invention, there is provided theequipment for treating an ammonium containing liquid according to thetenth aspect, wherein the nitrate reduction tank has a structure ofbringing the ammonium containing liquid into contact with pellets towhich the heterotrophic denitrifying bacteria are attached to beimmobilized, and the anaerobic ammonium oxidation tank has a structureof bringing the ammonium containing liquid treated in the nitratereduction tank into contact with pellets to which the anaerobic ammoniumoxidizing bacteria are attached to be immobilized.

By entrapping immobilization or attachment immobilization ofheterotrophic denitrifying bacteria or anaerobic ammonium oxidizingbacteria as described above, the equipment for treating an ammoniumcontaining liquid can have performance easily maintained anddenitrification capability improved.

In the aforementioned equipment for treating an ammonium containingliquid of the present invention, the nitrate reduction tank and theanaerobic ammonium oxidation tank preferably have a cell amount ratiocontrol device of controlling the number of cells of the heterotrophicdenitrifying bacteria to 10 to 1,000 times the number of cells of theanaerobic ammonium oxidizing bacteria. The nitrate reduction tank andthe anaerobic ammonium oxidation tank also preferably have a C/NO₃—Nratio control device of controlling the C/NO₃—N ratio of theconcentration C of the organic carbon contained in or added to theammonium containing liquid to the concentration NO₃—N of nitratenitrogen contained in or added to the ammonium containing liquid to 0.5to 2.5. This can promote stable high-speed denitrification of anammonium containing liquid in the equipment for treating an ammoniumcontaining liquid.

According to a fifteenth aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to the tenth aspect, wherein the nitrate reduction tank andthe anaerobic ammonium oxidation tank are carried out in one anaerobictank.

In the present invention, in particular, nitrate reduction treatment andanaerobic ammonium oxidation treatment do not have to be separatelycarried out insofar as each treatment is not prevented. Whenheterotrophic denitrifying bacteria and anaerobic ammonium oxidizingbacteria are present in one anaerobic tank and each of the treatments iscarried out for an ammonium containing liquid in the one tank, the sameeffects as in the separate treatments can be obtained.

The aforementioned anaerobic tank preferably has a structure of bringingthe ammonium containing liquid into contact with pellets in which theheterotrophic denitrifying bacteria are entrapped to be immobilized andpellets in which the anaerobic ammonium oxidizing bacteria are entrappedto be immobilized. The anaerobic tank may have a structure of bringingthe ammonium containing liquid into contact with pellets in which theheterotrophic denitrifying bacteria and the anaerobic ammonium oxidizingbacteria are entrapped to be immobilized. Further, the anaerobic tankmay have a structure of bringing the ammonium containing liquid intocontact with pellets to which the heterotrophic denitrifying bacteriathat reduce the nitrate to nitrite are attached to be immobilized andpellets to which the anaerobic ammonium oxidizing bacteria are attachedto be immobilized. The anaerobic tank may have a structure of bringingthe ammonium containing liquid brought into contact with pellets towhich the heterotrophic denitrifying bacteria and the anaerobic ammoniumoxidizing bacteria are attached to be immobilized.

Here, the anaerobic tank preferably has a cell amount ratio controldevice of controlling the number of cells of the heterotrophicdenitrifying bacteria to 10 to 1,000 times the number of cells of theanaerobic ammonium oxidizing bacteria. The anaerobic tank preferably hasa C/NO₃—N ratio control device of controlling the C/NO₃—N ratio of theconcentration C of the organic carbon contained in or added to theammonium containing liquid to the concentration NO₃—N of nitratenitrogen contained in or added to the ammonium containing liquid to 0.5to 2.5.

According to a twenty-second aspect of the present invention, to attainthe aforementioned object, there is provided a process for treating anammonium containing liquid by anaerobically biologically denitrifyingammonium in the ammonium containing liquid, the process comprisingadding a certain concentration of nitrate to an anaerobic ammoniumoxidation tank from a nitrate storage tank with the nitrate stored whenthe ammonium containing liquid is brought into contact withheterotrophic denitrifying bacteria and anaerobic ammonium oxidizingbacteria in the anaerobic ammonium oxidation tank to carry out thebiological denitrification.

If a part of ammonium in an ammonium containing liquid is converted tonitrite by nitrite-type nitrification reaction using nitrifyingbacteria, and the converted nitrite and the remaining ammonium aredenitrified by anaerobic ammonium oxidizing bacteria, in a conventionalmanner, the concentration of nitrite to be reacted with ammonium tendsto vary over time. Because of this, according to the present invention,a certain concentration of nitrate is stored in the nitrate storagetank, and a certain concentration of nitrate is added to the anaerobicammonium oxidation tank as a biological treatment tank from the nitratestorage tank.

Specifically, when a certain concentration of nitrate is added from thenitrate storage tank, the added nitrate can be converted to nitrite byheterotrophic denitrifying bacteria using, as a hydrogen donor, a BODcomponent in an ammonium containing liquid flowing into the anaerobicammonium oxidation tank. Consequently, the concentration of nitrite asan instable element can be stable, and thus nitrite and ammonium can besimultaneously denitrified by anaerobic ammonium oxidizing bacteria in astable manner. Furthermore, since nitrate inexpensive than nitrite isadded, the running cost necessary for the treatment can be reduced.

Here, a certain concentration of nitrate stored in the nitrate storagetank may be nitrate of a naturally occurring substance or chemicallysynthesized substance such as nitrate metal salt, or may be nitratebiologically produced by nitrifying bacteria in a nitrification tank. Itis basically enough only if a certain concentration of nitrate can beadded to the anaerobic ammonium oxidation tank from the nitrate storagetank.

According to a twenty-third aspect of the present invention, to attainthe aforementioned object, there is provided a process for treating anammonium containing liquid by anaerobically biologically denitrifyingammonium in the ammonium containing liquid, the process comprisingadding a certain concentration of nitrate to an anaerobic ammoniumoxidation tank from a nitrate storage tank with the nitrate stored, andadding a certain concentration of an organic substance to the anaerobicammonium oxidation tank from an organic substance storage tank with theorganic substance stored when the ammonium containing liquid is broughtinto contact with heterotrophic denitrifying bacteria and anaerobicammonium oxidizing bacteria in the anaerobic ammonium oxidation tank tocarry out the biological denitrification.

If the amount of a BOD component in an ammonium containing liquid to betreated is small, specifically, the organic substance concentration issmall, the reaction of reducing nitrate to nitrite by heterotrophicdenitrifying bacteria is carried out with reduced reactivity. Because ofthis, according to the present invention, a certain concentration of anorganic substance is added in a necessary amount from the organicsubstance storage tank, in addition to a certain concentration ofnitrate. Consequently, nitrate added from the nitrate storage tank canbe constantly stably reduced to nitrite by heterotrophic denitrifyingbacteria in the anaerobic ammonium oxidation tank, and thus nitrite andammonium can be simultaneously denitrified by anaerobic ammoniumoxidizing bacteria in a more stable manner.

According to a twenty-fourth aspect of the present invention, there isprovided the process for treating an ammonium containing liquidaccording to the twenty-second or twenty-third aspect, furthercomprising measuring the ammonium nitrogen concentration in the ammoniumcontaining liquid, calculating the necessary amount of nitrate from themeasured ammonium nitrogen concentration, and controlling the amount ofa certain concentration of the nitrate added, based on the calculatednecessary amount of the nitrate.

According to the present invention, the necessary amount of nitrite iscalculated from the ammonium nitrogen concentration obtained bymeasurement for an ammonium containing liquid, and the amount of acertain concentration of nitrite added is controlled based on thecalculation results. Consequently, the amount of nitrite added can beappropriately controlled according to the ammonium concentration in anammonium containing liquid. The process is particularly effective whenthe ammonium concentration in an ammonium containing liquid varies. Theammonium nitrogen concentration in an ammonium containing liquid may bemeasured continuously or intermittently.

According to a twenty-fifth aspect of the present invention, there isprovided the process for treating an ammonium containing liquidaccording to the twenty-third aspect, further comprising measuring theammonium nitrogen concentration in the ammonium containing liquid,calculating the necessary amount of nitrate from the measured ammoniumnitrogen concentration, controlling the amount of a certainconcentration of the nitrate added from the nitrate storage tank, basedon the calculated necessary amount of the nitrate, and controlling theamount of a certain concentration of the organic substance added fromthe organic storage tank, so that the C/NO₃—N ratio of the organiccarbon concentration to the nitrate nitrogen concentration in theammonium containing liquid is 0.5 to 2.5.

According to the present invention, when a necessary amount of a certainconcentration of nitrate is added to the anaerobic ammonium oxidationtank from the nitrate storage tank in accordance with the measuredammonium nitrogen concentration in an ammonium containing liquid, theamount of a certain concentration of an organic substance added from theorganic substance storage tank is controlled in accordance with thenecessary amount of nitrate added, so that the C/NO₃—N ratio of theorganic carbon concentration to the nitrate nitrogen concentration inthe ammonium containing liquid is 0.5 to 2.5.

Consequently, nitrate is added to the anaerobic ammonium oxidation tankwhile maintaining a constantly stable C/NO₃—N ratio, a competition fornitrite in an ammonium containing liquid can be prevented betweenheterotrophic denitrifying bacteria and anaerobic ammonium oxidizingbacteria. Accordingly, since nitrate reduction reaction by heterotrophicdenitrifying bacteria and simultaneous denitrification of nitrite andammonium by anaerobic ammonium oxidizing bacteria can be carried out ina stable manner without being affected by the quality of an ammoniumcontaining liquid, constantly stable high-speed denitrification can becontinuously carried out.

According to a twenty-sixth aspect of the present invention, there isprovided the process for treating an ammonium containing liquidaccording to any one of the twenty-second to twenty-fifth aspects,further comprising measuring the volume of the ammonium containingliquid flowing into the anaerobic ammonium oxidation tank, andincreasing or decreasing the amount of a certain concentration of thenitrate added in proportion to an increase or decrease in the measuredinflow volume.

According to the present invention, once the amount of nitrate added isdetermined corresponding to the necessary amount of nitrate, the amountof nitrate added is increased or decreased in proportion to an increaseor decrease in the inflow volume of an ammonium containing liquid. Theamount of nitrate added corresponding to the necessary amount of nitratemay be determined by calculating the necessary amount of nitrate frommeasurement of the ammonium nitrogen concentration in the ammoniumcontaining liquid as in the twenty-fourth and twenty-fifth aspects.Consequently, the amount of nitrate added can be appropriatelycontrolled in accordance with the inflow volume of the ammoniumcontaining liquid, and the measurement and controlling can besimplified. The inflow volume of the ammonium containing liquid may bemeasured continuously or intermittently. This process is effective foran ammonium containing liquid having a constant ammonium concentrationsuch as a development waste liquid. By measuring not only the ammoniumnitrogen concentration in the ammonium containing liquid but also thevolume of the ammonium containing liquid flowing into the anaerobicammonium oxidation tank, and controlling the amount of nitrite added,based on both the ammonium nitrogen concentration and the inflow volume,the amount of nitrite added can be more accurately controlled.

According to a twenty-seventh aspect of the present invention, there isprovided the process for treating an ammonium containing liquidaccording to the twenty-second or twenty-third aspect, furthercomprising increasing or decreasing the amount of the nitrate added tothe anaerobic ammonium oxidation tank from the nitrate storage tank,measuring an increase or decrease in the production rate (L/min) ofnitrogen gas produced in the anaerobic ammonium oxidation tank when theamount is increased or decreased, and controlling the amount of acertain concentration of the nitrate added with reference to, as thenecessary amount of nitrate, an amount that does not allow the gasproduction rate to be increased or decreased in direct proportion to anincrease or decrease in the amount of the nitrate added.

The process of the present invention controls the addition amount of acertain concentration of nitrate stored in the nitrate storage tank inaccordance with the production rate of gas produced in the anaerobicammonium oxidation tank, and thus is effective for controlling theamount of nitrate added concurrently with an increase or decrease in thetreatment load such as an increase or decrease in the ammoniumconcentration in the ammonium containing liquid or an increase ordecrease in the volume of the liquid flowing into the anaerobic ammoniumoxidation tank.

Specifically, in the anaerobic ammonium oxidation tank, ammonium isreacted with nitrite in the presence of anaerobic ammonium oxidizingbacteria to produce nitrogen gas. The production rate of the nitrogengas is increased or decreased concurrently with an increase or decreasein the treatment load such as an increase or decrease in the ammoniumconcentration or an increase or decrease in the inflow volume. Forexample, when the nitrogen gas production rate is increased as theamount of nitrate added is increased, the amount of nitrate added may beinsufficient. Thus, the amount of nitrate added is repeatedly increaseduntil the gas production rate is not increased. When the gas productionrate is not increased even if the amount of nitrate added is increased,the amount of nitrate added is excessive, and anaerobic ammoniumoxidizing bacteria may have reduced activity. Thus, the amount ofnitrate added is decreased until the gas production rate is decreased.The amount of nitrate added is repeatedly increased or decreased in thismanner to find an amount of nitrate added which does neither increasenor decrease the gas production rate. With reference to such an amountas the necessary amount of nitrate, the amount of nitrate added iscontrolled. This allows the amount of nitrate added to be appropriatelycontrolled, even if the ammonium nitrogen concentration in the ammoniumcontaining liquid or the inflow volume of the liquid is not measured,and furthermore allows the amount of nitrate added to be controlledconcurrently with an increase or decrease in the treatment load such asan increase or decrease in the ammonium concentration or an increase ordecrease in the inflow volume.

According to a twenty-eighth aspect of the present invention, to attainthe aforementioned object, there is provided equipment for treating anammonium containing liquid by anaerobically biologically denitrifyingammonium in the ammonium containing liquid, the equipment comprising anaerobic ammonium oxidation tank in which heterotrophic denitrifyingbacteria and anaerobic ammonium oxidizing bacteria are present, aninflow section of allowing the ammonium containing liquid to flow intothe anaerobic ammonium oxidation tank, a discharge section ofdischarging the liquid treated in the anaerobic ammonium oxidation tank,a nitrate storage tank of storing a certain concentration of nitrate, anitrate addition device of adding nitrate to the anaerobic ammoniumoxidation tank from the nitrate storage tank, and a nitrate additionamount control device of controlling the amount of the nitrate added.

According to a twenty-ninth aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to the twenty-eighth aspect, further comprising an organicsubstance storage tank of storing a certain concentration of an organicsubstance, an organic substance addition device of adding the organicsubstance to the anaerobic ammonium oxidation tank from the organicsubstance storage tank, and an organic substance addition amount controldevice of controlling the amount of the organic substance added.

In the twenty-eighth and twenty-ninth aspects, the aforementionedprocesses for treating an ammonium containing liquid according to thetwenty-second and twenty-third aspects are embodied in equipment. Theequipment can treat an ammonium containing liquid constantly stably andthus can provide a treated liquid with high quality constantly stably.

According to a thirtieth aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to the twenty-eighth or twenty-ninth aspect, furthercomprising a concentration measurement device of measuring the ammoniumnitrogen concentration in the ammonium containing liquid, wherein thenitrate addition amount control device controls the amount of thenitrate added, based on the measurement results from the concentrationmeasurement device. Consequently, a certain concentration of nitrate isadded to the anaerobic ammonium oxidation tank in an appropriatelycontrolled necessary amount by the nitrate addition amount controldevice. For this reason, the process is effective when the ammoniumconcentration in an ammonium containing liquid varies, and can furtherreduce the running cost necessary for the treatment.

According to a thirty-first aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to the twenty-ninth aspect, wherein the organic substanceaddition amount control device controls the amount of the organicsubstance added, based on the amount of the nitrate added from thenitrate addition amount control device, so that the C/NO₃—N ratio of theorganic carbon concentration to the nitrate nitrogen concentration inthe ammonium containing liquid is 0.5 to 2.5. Consequently, even whenthe ammonium concentration or organic substance concentration in anammonium containing liquid varies, ammonium in the ammonium containingliquid can be effectively treated.

According to a thirty-second aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to the twenty-eighth or twenty-ninth aspect, furthercomprising: an inflow volume measurement device of measuring the volumeof the ammonium containing liquid flowing into the anaerobic ammoniumoxidation tank, and a control device controls the amount of the nitrateadded, based on the measurement results from the inflow volumemeasurement device. Consequently, the amount of nitrate added iscontrolled to be a necessary amount of nitrate, based on the volume ofan ammonium containing liquid flowing into the anaerobic ammoniumoxidation tank. This process is thus effective for an ammoniumcontaining liquid having a constant ammonium concentration such as adevelopment waste liquid.

According to a thirty-third aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to the twenty-eighth or twenty-ninth aspect, furthercomprising a gas production rate measurement device of measuring anincrease or decrease in the production rate (L/min) of nitrogen gasproduced in the anaerobic ammonium oxidation tank when the amount of thenitrate added by the nitrate addition device is increased or decreased,wherein the nitrate addition amount control device controls the amountof the nitrate added, based on the measurement results from the gasproduction rate measurement device.

The process of the present invention controls the amount of nitrateadded by the nitrate addition amount control device to a necessaryamount of nitrate, based on the production rate of nitrogen gas producedin the anaerobic ammonium oxidation tank and measured by the gasproduction measurement device, and thus is effective for controlling theamount of nitrate added concurrently with an increase or decrease in thetreatment load such as an increase or decrease in the ammoniumconcentration in the ammonium containing liquid or an increase ordecrease in the volume of the liquid flowing into the anaerobic ammoniumoxidation tank.

According to a thirty-fourth aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to any one of the twenty-eighth to thirty-third aspects,wherein the anaerobic ammonium oxidation tank has a removable cartridgestructure and comprises a plurality of connection sections for theinflow section, the discharge section, and the addition device, and aplurality of the anaerobic ammonium oxidation tanks are attached to theinflow section, the discharge section, and the addition device.

According to the present invention, in the equipment for treating anammonium containing liquid, the anaerobic ammonium oxidation tanks havea removable cartridge structure, comprise a plurality of the connectionsections, respectively, and thus can be removably attached to the inflowsection, the discharge section, and the addition device. For thisreason, an ammonium containing liquid can be treated in the multipleanaerobic ammonium oxidation tanks by rotation, or one of the anaerobicammonium oxidation tanks can be used as an anaerobic ammonium oxidationtank reserved for emergency. Since the anaerobic ammonium oxidationtanks have a removable cartridge structure in this manner, whenheterotrophic denitrifying bacteria or anaerobic ammonium oxidizingbacteria have reduced activity or are killed in one of the anaerobicammonium oxidation tanks, the anaerobic ammonium oxidation tank can beeasily exchanged with another anaerobic ammonium oxidation tank, or areserved anaerobic ammonium oxidation tank can be used instead.

According to a thirty-fifth aspect of the present invention, to attainthe aforementioned object, there is provided equipment for treating anammonium containing liquid by biologically denitrifying ammonium in theammonium containing liquid, the equipment comprising a nitrificationtank of nitrifying ammonium in the ammonium containing liquid intonitrate by nitrifying bacteria, and an anaerobic ammonium oxidation tankof carrying out nitrate reduction treatment of reducing nitrate obtainedin the nitrification tank to nitrite by heterotrophic denitrifyingbacteria using an organic substance in the ammonium containing liquid asa hydrogen donor, and of simultaneously denitrifying nitrite produced bythe nitrate reduction treatment and ammonium in the ammonium containingliquid by anaerobic ammonium oxidizing bacteria.

The equipment for treating an ammonium containing liquid of the presentinvention carries out nitrification treatment of oxidizing ammonium inthe ammonium containing liquid to nitrate in the nitrification tank. Theequipment reduces nitrate produced in the nitrification tank to nitriteby heterotrophic denitrifying bacteria using an organic substance in theammonium containing liquid as a hydrogen donor, and carries outanaerobic ammonium oxidation treatment of denitrifying the producednitrite and ammonium in the ammonium containing liquid in the anaerobicammonium oxidation tank. This is because it is difficult for nitrifyingbacteria carrying out nitrification reaction to terminate the reactionwhen ammonium is converted to nitrite, due to the presence of ammoniumoxidizing bacteria of oxidizing ammonium to nitrite and nitriteoxidizing bacteria of oxidizing nitrite to nitrate. According to thepresent invention, a conventional nitrite-type nitrification reaction isnot carried out, but a nitrate-type nitrification treatment of oxidizingammonium to nitrate is carried out in the nitrification tank does not,and the resulting nitrate is reduced to nitrite by heterotrophicdenitrifying bacteria using an organic substance in an ammoniumcontaining liquid as a hydrogen donor in the anaerobic ammoniumoxidation tank. Consequently, the concentration of nitrite reacted withammonium is not changed over time. Thus, when nitrite obtained in thismanner and ammonium in the ammonium containing liquid are simultaneouslydenitrified by anaerobic ammonium oxidizing bacteria, nitrite andammonium can be denitrified at a preferable ratio between them.Accordingly, the ammonium containing liquid can be treated in a stablemanner. The nitrification treatment may be carried out before or afterthe anaerobic ammonium oxidation treatment. The anaerobic ammoniumoxidation treatment can be carried out by bypassing or circulatingwastewater or a nitrified liquid.

According to a thirty-sixth aspect of the present invention, to attainthe aforementioned object, there is provided equipment for treating anammonium containing liquid by biologically denitrifying ammonium in theammonium containing liquid, the equipment comprising a nitrificationtank of primarily separating the ammonium containing liquid into twoseparated ammonium containing liquids, and nitrifying ammonium in one ofthe separated ammonium containing liquids to nitrate by nitrifyingbacteria; a denitrification tank of further secondarily separating thenitrified liquid obtained in the nitrification tank into two separatednitrified liquids, mixing one of the separated nitrified liquids withthe other primarily separated ammonium containing liquid, and carryingout denitrification treatment of nitrate in the separated nitrifiedliquid by denitrifying bacteria using an organic substance in theseparated ammonium containing liquid as a hydrogen donor; and ananaerobic ammonium oxidation tank of mixing the other secondarilyseparated nitrified liquid with the denitrified liquid from thedenitrification tank and carrying out nitrate reduction treatment ofreducing nitrate contained in the separated nitrified liquid to nitriteby heterotrophic denitrifying bacteria using an organic substance in thedenitrified liquid as a hydrogen donor, and of simultaneouslydenitrifying nitrite produced by the nitrate reduction treatment andammonium in the denitrified liquid by anaerobic ammonium oxidizingbacteria.

In the equipment according to the thirty-sixth aspect of the presentinvention, unlike the equipment according to the thirty-fifth aspect,the anaerobic ammonium oxidation tank does not carry out reductiontreatment of reducing nitrate produced in the nitrification tank tonitrite together with denitrification treatment of nitrite and ammonium.Instead, the aforementioned reduction treatment is carried out in thedenitrification tank, and the denitrified liquid is allowed to flow intothe anaerobic ammonium oxidation tank. The equipment is suitable when alarge amount of an organic substance is contained in an ammoniumcontaining liquid. If the ammonium containing liquid contains a highconcentration of an organic substance concentration, the organicsubstance inhibits ammonium oxidation reaction in anaerobic ammoniumoxidation treatment. On the contrary, when the organic substanceconcentration is low, reduction reaction from nitrate does not proceedin anaerobic ammonium oxidation treatment. Thus, by allowing the liquidsubjected to denitrification treatment in the denitrification tank andammonium in the ammonium containing liquid to flow to the anaerobicammonium oxidation tank, anaerobic ammonium oxidation treatment can becarried out using a certain concentration of an organic substance.

Specifically, in the line between the nitrification tank and thedenitrification tank, common nitrification and denitrification treatmentis carried out, and nitrate is converted into nitrogen gas using anorganic substance in an ammonium containing liquid as a hydrogen donor.Thus, not only the organic substance in the ammonium containing liquidbut also the reaction burden on the anaerobic ammonium oxidation tankcan be reduced. Consequently, the organic component can be made stablein anaerobic ammonium oxidation treatment, and nitrite and ammonium inthe ammonium containing liquid can be simultaneously denitrified byanaerobic ammonium oxidizing bacteria in a stable manner.

According to a thirty-seventh aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to the thirty-fifth or thirty-sixth aspect, wherein theheterotrophic denitrifying bacteria are controlled to have cells 10 to1,000 times of cells that the anaerobic ammonium oxidizing bacteriahave.

According to the present invention, since nitrate reduction treatmentand anaerobic ammonium oxidation treatment are carried out bycontrolling the ratio in number of cells of heterotrophic denitrifyingbacteria to anaerobic ammonium oxidizing bacteria to make these bacterialive symbiotically and coexist in a preferable state, the nitrogenremoval ratio can be improved.

According to a thirty-eighth aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to any one of the thirty-fifth to thirty-seventh aspects ofthe present invention, wherein the organic substance is added to theanaerobic ammonium oxidation tank.

If the organic substance concentration in an ammonium containing liquidto be treated is small, the reaction of reducing nitrate to nitrite byheterotrophic denitrifying bacteria is carried out with reducedreactivity. Because of this, according to the present invention, acertain concentration of the organic substance is added in a necessaryamount. Consequently, nitrate can be constantly stably reduced tonitrite by heterotrophic denitrifying bacteria in the anaerobic ammoniumoxidation tank, and thus nitrite and ammonium can be simultaneouslydenitrified by anaerobic ammonium oxidizing bacteria in a more stablemanner in anaerobic ammonium oxidation treatment.

According to a thirty-ninth aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to any one of the thirty-fifth to thirty-eighth aspects,wherein the C/NO₃—N ratio of the concentration C of the organic carboncontained in and/or added to the ammonium containing liquid to theconcentration NO₃—N of nitrate nitrogen contained in and/or added to theammonium containing liquid is controlled to be 0.5 to 2.5 in theanaerobic ammonium oxidation tank.

In the ammonium oxidation tank, efficiency in the aforementioned nitratereduction treatment and anaerobic ammonium oxidation treatment isinfluenced by the ratio of the organic carbon concentration to thenitrate nitrogen concentration in an ammonium containing liquid.Specifically, when the C/NO₃—N ratio of the organic carbon concentrationC to the nitrate nitrogen concentration NO₃—N in the inflow ammoniumcontaining liquid is controlled to be 0.5 to 2.5, nitrite can beaccumulated easily in nitrate reduction treatment by heterotrophicdenitrifying bacteria, and the produced nitrite and ammonium can beeasily denitrified by anaerobic ammonium oxidizing bacteria.

According to the present invention, the C/NO₃—N ratio is constantlystable in the anaerobic ammonium oxidation tank, a competition fornitrite in an ammonium containing liquid can be controlled in a stablemanner between heterotrophic denitrifying bacteria and anaerobicammonium oxidizing bacteria. Accordingly, since nitrate reductionreaction by heterotrophic denitrifying bacteria and simultaneousdenitrification of nitrite and ammonium by anaerobic ammonium oxidizingbacteria can be carried out in a stable manner, constantly stablehigh-speed denitrification can be continuously carried out.

According to a fortieth aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to any one of the thirty-sixth to thirty-ninth aspects of thepresent invention, wherein the denitrification tank is provided asmultiple tanks.

According to the present invention, by providing the denitrificationtank as multiple tanks and allowing a liquid to flow therein stepwise,anaerobic ammonium oxidation bacteria can be prevented from beinginhibited by an organic substance.

According to a forty-first aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to any one of the thirty-fifth to fortieth aspects of thepresent invention, wherein the nitrification tank is provided asmultiple tanks.

According to the present invention, since the nitrification tank isprovided as multiple tanks, ammonium can be efficiently nitrified, and anitrified liquid can be supplied to the anaerobic ammonium oxidationtank. In particular, the equipment is effective for high-concentrationammonium wastewater since nitrification of the wastewater proceeds onlywith difficulty.

According to a forty-second aspect of the present invention, there isprovided the equipment for treating an ammonium containing liquidaccording to any one of the thirty-fifth to forty-first aspects of thepresent invention, wherein the anaerobic ammonium oxidation tank isprovided as multiple tanks.

According to the present invention, by providing the anaerobic ammoniumoxidation tank as multiple tanks and allowing a liquid to flow thereinstepwise, anaerobic ammonium oxidation bacteria can be prevented frombeing inhibited by an organic substance.

As described above, the process and equipment of the present inventioncan stably carry out anaerobic ammonium oxidation treatment that allowshigh-speed denitrification without being affected by the change in theconcentrations of nitrogen components in an ammonium containing liquidto be treated or the change in the nitrogen form between nitrate andnitrite.

The process and equipment of the present invention can treat an ammoniumcontaining liquid constantly stably and thus can provide a treatedliquid with constantly stable and high quality. Further, the process andequipment of the present invention employ nitrate inexpensive thannitrite, and thus can reduce the cost necessary for the treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relation between the C/NO₃—N ratio and thenitrogen removal ratio in a first test of demonstrating the presentinvention;

FIG. 2 is a graph showing the correlation between the nitrogen removalratio and the ratio of the number of cells of heterotrophic denitrifyingbacteria to the number of cells of anaerobic ammonium oxidizing bacteriain a second test of demonstrating the present invention;

FIG. 3A is a side view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a firstembodiment of the present invention;

FIG. 3B is a side view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a secondembodiment of the present invention;

FIG. 3C is a side view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a thirdembodiment of the present invention;

FIG. 3D is a side view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a fourthembodiment of the present invention;

FIG. 4A is an oblique perspective view showing an outline of one exampleof entrapping immobilization pellets applied to the present invention;

FIG. 4B is an oblique perspective view showing an outline of anotherexample of entrapping immobilization pellets applied to the presentinvention;

FIG. 4C is an oblique perspective view showing an outline of stillanother example of entrapping immobilization pellets applied to thepresent invention;

FIG. 5 is a plan view showing a schematic configuration of equipment fortreating an ammonium containing liquid according to a fifth embodimentof the present invention;

FIG. 6 is a plan view showing a schematic configuration of equipment fortreating an ammonium containing liquid according to a sixth embodimentof the present invention;

FIG. 7 is a plan view showing a schematic configuration of equipment fortreating an ammonium containing liquid according to a seventh embodimentof the present invention;

FIG. 8 is a plan view showing a schematic configuration of equipment fortreating an ammonium containing liquid according to an eighth embodimentof the present invention;

FIG. 9 is a plan view showing a schematic configuration of equipment fortreating an ammonium containing liquid according to a ninth embodimentof the present invention;

FIG. 10 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a tenthembodiment of the present invention;

FIG. 11 is a flow chart showing a control program in a nitrate andorganic substance automatic control system by nitrogen gas generationmonitoring;

FIG. 12 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to an eleventhembodiment of the present invention;

FIG. 13 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a twelfthembodiment of the present invention;

FIG. 14 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a thirteenthembodiment of the present invention;

FIG. 15 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a fourteenthembodiment of the present invention;

FIG. 16 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a fifteenthembodiment of the present invention;

FIG. 17 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a sixteenthembodiment of the present invention;

FIG. 18 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a seventeenthembodiment of the present invention;

FIG. 19 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to an eighteenthembodiment of the present invention;

FIG. 20 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a nineteenthembodiment of the present invention;

FIG. 21 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a twentiethembodiment of the present invention; and

FIG. 22 is a plan view showing a schematic configuration of equipmentfor treating an ammonium containing liquid according to a twenty-firstembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first feature of the present invention is that nitrate contained in oradded to an ammonium containing liquid to be treated is reduced tonitrite by heterotrophic denitrifying bacteria, and the nitrite andammonium are denitrified by anaerobic ammonium oxidizing bacteria.

A second feature of the present invention is described as follows. Thepresent inventors have found that, in a conventional anaerobic ammoniumoxidation reaction, (i) too high a concentration of nitrite suppliedinvolves a risk in treatment due to toxicity of nitrite, and (ii) anorganic substance highly inhibits anaerobic ammonium oxidizing bacteria.In order to solve these problems, the inventors have found that completenitrification reaction is carried out in a nitrification tank, theresulting nitrate solution is supplied to an anaerobic ammoniumoxidation tank, and denitrification stably proceeds in a system in whichanaerobic ammonium oxidizing bacteria and heterotrophic denitrifyingbacteria coexist.

The supplied nitrate is reduced to nitrite by heterotrophic denitrifyingbacteria, using an organic substance (also called “organic carbon”) as ahydrogen donor, and the produced nitrite is immediately denitrifiedtogether with ammonium by anaerobic ammonium oxidizing bacteria.Consequently, nitrite is not accumulated, and toxic inhibition bynitrite is prevented. The organic substance in wastewater is used fornitrate reduction reaction, and anaerobic ammonium oxidizing bacteriaare prevented from being inhibited by the organic substance. Waterflowing into the anaerobic ammonium oxidation vessel is preferablycontrolled so that the nitrate nitrogen concentration is once to twicethe ammonium nitrogen concentration. Nitrate is reduced to nitrite byheterotrophic denitrifying bacteria. Anaerobic ammonium oxidizingbacteria compete with heterotrophic denitrifying bacteria for thenitrite. The present inventors have discovered the best process fortreating an ammonium containing liquid characterized by the followingtwo features in order to give priority to reaction by anaerobic ammoniumoxidizing bacteria in this case.

(1) In the present invention, when the C/NO₃—N ratio of theconcentration C of the organic carbon contained in or added to an inflowammonium containing liquid to the concentration NO₃—N of nitratenitrogen contained in or added to the inflow ammonium containing liquidis controlled to be 0.5 to 2.5, reduction treatment by heterotrophicdenitrifying bacteria is insufficient, and thus nitrite can be easilyaccumulated without being reduced to nitrogen gas, and the producednitrite and ammonium can be easily denitrified by anaerobic ammoniumoxidizing bacteria.

(2) The aforementioned heterotrophic denitrifying bacteria and anaerobicammonium oxidizing bacteria are preferably entrapped or attached to beimmobilized for use. When these bacteria are immobilized so that theheterotrophic denitrifying bacteria have cells 10 to 1,000 times ofcells that the anaerobic ammonium oxidizing bacteria have, thesebacteria live symbiotically or coexist in a preferable state, andnitrate reduction treatment and anaerobic ammonium oxidation treatmentare activated, and thus the rate of removing nitrogen from an ammoniumcontaining liquid can be improved.

First, the present inventors have carried out a first test fordemonstrating the feature (1). In the first test, synthetic wastewateras an ammonium containing liquid was continuously treated with pelletsin which 2×10⁶ cells/mL of heterotrophic denitrifying bacteria and 2×10⁵cells/mL of anaerobic ammonium oxidizing bacteria were immobilized. Onemonth later, the treatment was made stable, and the C/NO₃—N ratio andthe denitrification rate were measured.

In the first test, pellets obtained by forming a polyethylene glycoldiacrylate material with a microorganism entrapped to be immobilizedinto 3 mm-square cubes were used for entrapping immobilization. A 1 Lreaction tank was packed with the pellets thus obtained at a packingratio of 20%. The synthetic wastewater was continuously supplied to thereaction tank and treated.

The above-described synthetic wastewater used was synthetic wastewatercontrolled to have a ratio of the ammonium nitrogen concentration to thenitrate concentration of 1:1 and a total nitrogen concentration T-N of80 mg/L, and controlled to have a C/NO₃—N ratio of 1 by addition ofsodium acetate as an organic source (C).

The reaction tank started operation at a treatment load of 1.2kg-N/m³/day. One month later, the wastewater was treated to achieve aT-N removal ratio of 82%, and the treatment was made stable. Then, thetank was operated while changing the C/NO₃—N ratio to 0.2 to 4, and therelation between the C/NO₃—N ratio and the T-N removal ratio wasexamined. The results are shown in FIG. 1. FIG. 1 is a graph showing therelation between the C/NO₃—N ratio and the T-N removal ratio in thefirst test.

The graph of FIG. 1 shows that a high T-N removal ratio of 50% or moreis obtained when the C/NO₃—N ratio is 0.5 to 2.5, in particular 1 to 2.On the other hand, when the C/NO₃—N ratio is more than 2.5, the T-Nremoval ratio is rapidly reduced. This is presumably becausedenitrification is carried out primarily by heterotrophic denitrifyingbacteria, and reaction using an organic substance as an electron donorproceeds, and thus anaerobic ammonium oxidation reaction by anaerobicammonium oxidizing bacteria is inhibited. Accordingly, in the presentinvention, efficient denitrification treatment can be carried out in astable manner by carrying out nitrate reduction treatment and anaerobicammonium oxidation treatment with a C/NO₃—N ratio controlled to 0.5 to2.5, and preferably 1 to 2. As an organic substance used for controllingthe C/NO₃—N ratio, methanol, molasses, or acetic acid is preferable.

Next, the present inventors have carried out a second test fordemonstrating the aforementioned feature (2). In the second test,synthetic wastewater as an ammonium containing liquid was continuouslytreated with pellets in which cells of heterotrophic denitrifyingbacteria and cells of anaerobic ammonium oxidizing bacteria wereimmobilized. One month later, the treatment was made stable, and theC/NO₃—N ratio and the denitrification rate were measured.

In the second test, pellets obtained by forming a polyethylene glycoldiacrylate material with a microorganism entrapped to be immobilizedinto 3 mm-square cubes were used for entrapping immobilization as in thefirst test. A 1 L reaction tank was packed with the pellets thusobtained at a packing ratio of 20%. The synthetic wastewater wascontinuously supplied to the reaction tank and treated.

The above-described synthetic wastewater used was synthetic wastewatercontrolled to have a ratio of the ammonium nitrogen concentration to thenitrate concentration of 1:1 and a total nitrogen concentration T-N of80 mg/L, and controlled to have a C/NO₃—N ratio of 1 by addition ofsodium acetate as an organic carbon (C).

The reaction tank started operation at a treatment load of 1.2kg-N/m³/day. One month later, the treatment was made stable, and thequality of the treated water (specifically, nitrogen removal ratio) wasevaluated. The results are shown in FIG. 2. FIG. 2 is a graph showingthe correlation between the nitrogen removal ratio and the ratio of thenumber of cells of heterotrophic denitrifying bacteria to the number ofcells of anaerobic ammonium oxidizing bacteria in the second test.

The graph of FIG. 2 shows that a high T-N removal ratio of 50% or moreis obtained when using pellets in which heterotrophic denitrifyingbacteria having cells 10 to 1,000 times of cells that anaerobic ammoniumoxidizing bacteria have are immobilized. On the other hand, if thenumber of cells of heterotrophic denitrifying bacteria is too small, theT-N removal ratio is low. Or if the number of cells is too large, theT-N removal ratio tends to be reduced. This is because heterotrophicdenitrifying bacteria and anaerobic ammonium oxidizing bacteria livesymbiotically or coexist at an appropriate ratio between them, and thusa competition for the produced nitrite between treatments by the twokinds of bacteria is controlled in a well-balanced manner, and nitrogenremoval is further activated. The same inclination was observed inattachment immobilization at the above-described ratio in number ofcells between these bacteria. Description for such immobilization isomitted.

Preferred embodiments of the process and equipment for treating anammonium containing liquid of the present invention will be described indetail below with reference to the accompanying drawings.

[1] First, embodiments in which nitrite produced by nitrate reductiontreatment is supplied to an anaerobic ammonium oxidation tank will bedescribed with reference to FIGS. 3A to 3D.

FIG. 3A is a side view showing a schematic configuration of equipment 10for treating an ammonium containing liquid according to a firstembodiment for implementing the present invention, and shows one exampleof equipment composed of a nitrate reduction tank 12 and an anaerobicammonium oxidation tank 14.

As shown in FIG. 3A, in the equipment 10 for treating an ammoniumcontaining liquid, an ammonium containing liquid containing ammonium andnitrate (hereinafter called “wastewater”) flows into the nitratereduction tank 12 through an inflow pipe 16. Here, the wastewater ispreferably controlled to have a C/NO₃—N ratio of 0.5 to 2.5. Forexample, the equipment may comprise a C/NO₃—N ratio control device (notshown) for measuring C/NO₃—N in the wastewater, and adding an organicsubstance such as methanol or molasses or nitrate nitrogen such as anitrate metal salt to the wastewater inside or outside the tank inaccordance with the measurement results.

In the nitrate reduction tank 12, heterotrophic denitrifying bacteriaare present, and nitrate in the inflow wastewater is reduced to nitriteusing an organic substance in the wastewater as a hydrogen donor. Thewastewater subjected to nitrate reduction treatment in the nitratereduction tank 12 in this manner flows into the anaerobic ammoniumoxidation tank 14, and nitrite and ammonium contained in the wastewaterare simultaneously denitrified by anaerobic ammonium oxidizing bacteriain the tank. The wastewater treated in this manner is discharged from adischarge pipe 18.

Heterotrophic denitrifying bacteria in the nitrate reduction tank 12 andanaerobic ammonium oxidizing bacteria in the anaerobic ammoniumoxidation tank 14 are preferably attachment immobilized or entrappingimmobilized.

Anaerobic ammonium oxidizing bacteria can be acclimatized using, as seedsludge, activated sludge or anaerobic digested sludge containinganaerobic ammonium oxidizing bacteria, as described in Lectures in JapanSociety on Water Environment 7th Symposium, 2004, p. 125. Anaerobicammonium oxidizing bacteria in the present specification refers to anybacteria containing ammonium and nitrite as substrates for anaerobicallybiologically denitrifying ammonium in an ammonium containing liquid.

An anaerobic ammonium oxidation tank in the present invention refers toan anaerobic ammonium oxidation tank for anaerobically biologicallydenitrifying ammonium in an ammonium containing liquid, which can beapplied to any biological denitrification treatment using bacteriacontaining ammonium and nitrite as substrates.

Although anaerobic ammonium oxidizing bacteria or the like may bemaintained as floating bacteria in the anaerobic ammonium oxidation tank14, the bacteria are preferably maintained in the tank as a biofilm inwhich anaerobic ammonium oxidizing bacteria or the like are attached toa packing material, or as immobilization pellets in which anaerobicammonium oxidizing bacteria or the like are immobilized in or to animmobilizing material.

The anaerobic ammonium oxidation tank 14 is packed with heterotrophicdenitrifying bacteria and anaerobic ammonium oxidizing bacteriamaintained as a biofilm preferably in an amount of 30 to 70 vol % whenthe tank is a fixed bed tank, or in an amount of 5 to 40 vol % when thetank is a suspended particle tank or an expansion bed tank. The packingmaterial used for the biofilm may be a material such as a nonwovencloth, plastic material, or sponge material, and may have various shapessuch as a plate-like shape, granular shape, and cylindrical shape.

Each bacteria can be immobilized by 1) attachment immobilization or 2)entrapping immobilization.

In the attachment immobilization 1), the ammonium removal ratio can beimproved by using pellets such as globular or cylindrical pellets ormaterials with many irregularities such as a material in the shape ofstrings, gels, or nonwoven clothes, because each bacteria are easilyattached to such pellets or materials.

The entrapping immobilization 2) is generally carried out by mixing amonomer or prepolymer as an immobilization material with bacteria to beimmobilized, and polymerizing the mixture to entrap and immobilize thebacteria. As the monomer material, acrylamide, methylenebisacrylamide,triacrylformal, or the like is preferable.

As the prepolymer material, polyethylene glycol diacrylate orpolyethylene glycol methacrylate is preferable, and a derivative thereofmay also be used. Entrapping immobilization pellets with manyirregularities such as globular or cylindrical entrapping pellets,string-shaped entrapping pellets, or nonwoven cloth entrapping pelletsbring an ammonium containing liquid such as wastewater into contact witheach bacteria efficiently, and thus the ammonium removal ratio can beimproved.

For example, Table 1 shows a typical composition example of entrappingimmobilization pellets in which heterotrophic denitrifying bacteria andanaerobic ammonium oxidizing bacteria are entrapped to be immobilized.

TABLE 1 Composition ratio Composition component (weight %) Anaerobicammonium oxidizing 15 bacteria concentrate (10⁷ cells/mL) Heterotrophicnitrifying bacteria 15 (10⁸ cells/mL) Polyethylene glycol diacrylate 10N,N,N′,N′-tetramethylethylenediamine 0.5 Potassium persulfate 0.25 Water59.25

A suspension having a composition of Table 1 starts to be polymerized byaddition of 0.25 part of potassium persulfate, and is gelled. The gel iscut into entrapping immobilization pellets with any size each.Entrapping immobilization pellets in the shape of rectangles or globespreferably have a size of 1 to 10 mm each.

FIGS. 4A to 4C are oblique perspective views showing an outline of eachexample of entrapping immobilization pellets applied to the presentinvention, in which some of the pellets are transparent.

In the present invention, as shown in FIG. 4A, pellets 50A in whichheterotrophic denitrifying bacteria 52,52 . . . are entrapped to beimmobilized and pellets 50B in which anaerobic ammonium oxidizingbacteria 54,54 . . . are entrapped to be immobilized can be separatelyprepared and used. As shown in FIG. 4B, pellets 50 in which a mixture ofheterotrophic denitrifying bacteria 52,52 . . . with anaerobic ammoniumoxidizing bacteria 54,54 . . . are entrapped to be immobilized can alsobe used. Further, as shown in FIG. 4C, pellets 50′ in which anaerobicammonium oxidizing bacteria 54,54 . . . are entrapped to be immobilizedin the center and heterotrophic denitrifying bacteria 52,52 . . . areentrapped to be immobilized around the anaerobic ammonium oxidizingbacteria and near the surface can also be used. When these pellets areused for the treatment equipment of the present invention, it ispreferable to control the amount of each pellets in each tank by a cellnumber ratio control device (not shown), so that the above-describedratio between the two kinds of bacteria is achieved, specifically,heterotrophic denitrifying bacteria have cells 10 to 1,000 times ofcells that anaerobic ammonium oxidizing bacteria have.

The equipment 10 for treating an ammonium containing liquid according tothe first embodiment shown in FIG. 3A preferably employs the pellets 50Aand 50B shown in FIG. 4A.

FIG. 3B is a side view showing a schematic configuration of equipment 20for treating an ammonium containing liquid according to a secondembodiment for implementing the present invention, and shows one exampleof equipment composed of an anaerobic ammonium oxidation tank. The sameapparatus or member as in the equipment 10 for treating an ammoniumcontaining liquid according to the first embodiment shown in FIG. 3Awill be described with the same reference numeral, and repetition of thesame description will be omitted. This also applies to third and fourthembodiments.

As shown in FIG. 3B, in the equipment 20 for treating an ammoniumcontaining liquid, wastewater containing ammonium and nitrate flows intothe anaerobic ammonium oxidation tank 14 through an inflow pipe 16.Here, the wastewater is preferably controlled to have a C/NO₃—N ratio of0.5 to 2.5, as in the aforementioned first embodiment. For example, theequipment may comprise a C/NO₃—N ratio control device (not shown) formeasuring C/NO₃—N in the wastewater, and adding an organic substancesuch as methanol or molasses or nitrate nitrogen such as a nitrate metalsalt to the wastewater inside or outside the tank in accordance with themeasurement results.

In the anaerobic ammonium oxidation tank 14, the aforementionedheterotrophic denitrifying bacteria and anaerobic ammonium oxidizingbacteria are present. These bacteria are preferably attachmentimmobilized or entrapping immobilized, and the entrapping immobilizedpellets shown in FIGS. 4A to 4C can be suitably used at a predeterminedratio between them. In the anaerobic ammonium oxidation tank 14, nitratein the inflow wastewater is reduced to nitrite by the heterotrophicdenitrifying bacteria using an organic substance as a hydrogen donor,and nitrite and ammonium in the inflow wastewater are simultaneouslydenitrified by the anaerobic ammonium oxidizing bacteria. The wastewatertreated in this manner is discharged to outside the system from adischarge pipe 18.

FIG. 3C is a side view showing a schematic configuration of equipment 30for treating an ammonium containing liquid according to a thirdembodiment of the present invention, and shows one example of equipmentcomprising an anaerobic tank 22 and an aerobic tank 24.

As shown in FIG. 3C, in the equipment 30 for treating an ammoniumcontaining liquid, wastewater containing ammonium flows into theanaerobic tank 22 through an inflow pipe 16. Here, the wastewater ispreferably controlled to have a C/NO₃—N ratio of 0.5 to 2.5, as in theaforementioned first and second embodiments. For example, the equipmentmay comprise a C/NO₃—N ratio control device (not shown) for measuringC/NO₃—N in the wastewater, and adding an organic substance such asmethanol or molasses or nitrate nitrogen such as a nitrate metal salt tothe wastewater inside or outside the tank in accordance with themeasurement results.

In the anaerobic tank 22, the aforementioned heterotrophic denitrifyingbacteria and anaerobic ammonium oxidizing bacteria are present. It ispreferable that each bacteria form entrapping immobilization pellets asshown in FIGS. 4A to 4C, and the tank be packed with the pellets.Accordingly, in the anaerobic tank 22, nitrate in the inflow wastewateris reduced to nitrite by the heterotrophic denitrifying bacteria usingan organic substance as a hydrogen donor, and nitrite and ammonium inthe inflow wastewater are simultaneously denitrified by the anaerobicammonium oxidizing bacteria. The wastewater treated in the anaerobictank 22 flows into the aerobic tank 24.

The aerobic tank 24 has nitrifying bacteria therein, and is aerated byan aeration unit 26 from below. The aerobic tank 24 is packed with thenitrifying bacteria in the state of attachment immobilization pellets,entrapping immobilization pellets, or floating activated sludge such asgranules.

A part of the water treated in the aerobic tank 24 is fed back to theanaerobic tank 22 from a discharge pipe 18 through a circulation line28, and nitrate remaining in the treated water is treated. Consequently,the wastewater can be efficiently treated by reuse of the treated waterin the anaerobic tank that needs nitrate. The returning volume in thecirculation line 28 is smaller than that in a conventionaldenitrification treatment, but a high denitrification rate can beachieved. The water treated in this manner is discharged to outside thesystem from the discharge pipe 18.

FIG. 3D is a side view showing a schematic configuration of equipment 40for treating an ammonium containing liquid according to a fourthembodiment of the present invention, and shows one example of equipmentcomprising an aerobic tank 24 and an anaerobic tank 22 in this orderfrom the upstream.

As shown in FIG. 3D, in the equipment 40 for treating an ammoniumcontaining liquid, wastewater containing ammonium flows into the aerobictank 24 through an inflow pipe 16. The aerobic tank 24 has nitrifyingbacteria therein, and is aerated by an aeration unit 26 from below. Theaerobic tank 24 is packed with the nitrifying bacteria in the state ofattachment immobilization pellets, entrapping immobilization pellets, orfloating activated sludge such as granules. In the aerobic tank 24, apart of ammonium in the inflow wastewater is oxidized to nitrate by thenitrifying bacteria. The wastewater containing ammonium and nitratetreated in this manner flows into the anaerobic tank 22.

In the anaerobic tank 22, the aforementioned heterotrophic denitrifyingbacteria and anaerobic ammonium oxidizing bacteria are present. It ispreferable that each bacteria form entrapping immobilization pellets asshown in FIGS. 4A to 4C, and the tank be packed with the pellets. Anorganic substance addition unit 32 is provided in the anaerobic tank 22,and the unit preferably adds an organic substance to the wastewaterflowing into the tank so that the wastewater has a C/NO₃—N ratio of 0.5to 2.5. For example, the equipment may comprise a C/NO₃—N ratio controldevice (not shown) for measuring C/NO₃—N in the wastewater, and addingan organic substance such as methanol or molasses or nitrate nitrogensuch as a nitrate metal salt to the wastewater inside or outside thetank in accordance with the measurement results.

In the anaerobic tank 22 thus configured, nitrate in the inflowwastewater is reduced to nitrite by the heterotrophic denitrifyingbacteria using an organic substance as a hydrogen donor, and nitrite andammonium in the inflow wastewater are simultaneously denitrified by theanaerobic ammonium oxidizing bacteria. The wastewater treated in theanaerobic tank 22 in this manner is discharged to outside the systemfrom a discharge pipe 18.

The aforementioned first to fourth embodiments are described takingbiological treatment by heterotrophic denitrifying bacteria as anexample of treatment of reducing nitrate to nitrite. The same effect canbe achieved when using a catalyst that reduces nitrate to nitrite, forexample, a Pd—Cu catalyst composed of an alloy of palladium and copper.In this case, the catalyst is preferably used in a nitrate reductiontank 12 in FIG. 3A, an anaerobic ammonium oxidation tank 14 in FIG. 3B,or an anaerobic tank 22 in FIGS. 3C and 3D. However, nitrate reductiontreatment by a catalyst must be carried out under the same conditions asin nitrate reduction treatment carried by the aforementionedheterotrophic denitrifying bacteria. Nitrate may be added to raw waterin advance, or may be added as in the case of the above sodium acetate.

[2] Next, embodiments of a process of supplying nitrate to an anaerobicammonium oxidation tank from a tank for storing a certain concentrationof nitrate will be described with reference to FIGS. 5 to 12.

The equipment for treating an ammonium containing liquid of the presentinvention shown in FIGS. 5 to 12 comprises a nitrate storage tank 112and an anaerobic ammonium oxidation tank 114 as basic constituents, andconstituents equipped with the basic constituents such as variousmeasurement devices and control devices, as shown in the followingvarious embodiments.

Accordingly, the nitrate storage tank 112 and the anaerobic ammoniumoxidation tank 114 as basic constituents will be described first, andthen various embodiments will be described.

The nitrate storage tank 112 has a structure that can store a solutionof a nitrate metal salt in a solvent (typically water) with a certainconcentration of nitrate added, or a powder of a nitrate metal saltcontrolled so that a certain concentration of nitrate is added. Thenitrate storage tank 112 has a structure in which a necessary amount ofnitrate appropriate for treating ammonium contained in an ammoniumcontaining liquid is added to the anaerobic ammonium oxidation tank 114by various measurements and controls. In this case, nitrate stored inthe nitrate storage tank 112 is not limited to a naturally occurringsubstance such as the aforementioned nitrate metal salt, or a chemicallysynthesized substance, but may be nitrate produced when biologicallynitrifying ammonium or nitrite. It is basically enough only if a certainconcentration of nitrate is stored in and stably added to the anaerobicammonium oxidation tank 114.

Heterotrophic denitrifying bacteria and anaerobic ammonium oxidizingbacteria are acclimatized in or introduced into the anaerobic ammoniumoxidation tank 114, and the tank is maintained in an anaerobicatmosphere.

The anaerobic ammonium oxidation tank 114 is, as described above, abiological treatment tank for anaerobically biologically denitrifyingammonium in an ammonium containing liquid. The anaerobic ammoniumoxidation tank 114 is preferably packed with entrapping immobilizationpellets containing anaerobic ammonium oxidizing bacteria in an amount asdescribed above, for example.

Here, the content, type, culturing method, and maintenance form ofvarious bacteria such as heterotrophic denitrifying bacteria andanaerobic ammonium oxidizing bacteria, and the form of entrappingimmobilization pellets may be the same as described above.

Entrapping immobilization pellets may be introduced into a reaction tanksuch as an anaerobic ammonium oxidation tank, as entrappingimmobilization pellets in which heterotrophic denitrifying bacteria aremixed with anaerobic ammonium oxidizing bacteria at the aforementionedratio shown in Table 1, or as pellets in which heterotrophicdenitrifying bacteria are entrapped to be immobilized and pellets inwhich anaerobic ammonium oxidizing bacteria are entrapped to beimmobilized, the two types of pellets separately prepared. Pellets inwhich anaerobic ammonium oxidizing bacteria are entrapped to beimmobilized at the center, and heterotrophic denitrifying bacteria areentrapped to be immobilized around the anaerobic ammonium oxidizingbacteria and near the surface can also be used in the present invention.

FIG. 5 shows equipment 110 for treating an ammonium containing liquidaccording to a fifth embodiment, which is constituted by an anaerobicammonium oxidation tank 114 in an anaerobic atmosphere in whichheterotrophic denitrifying bacteria and anaerobic ammonium oxidizingbacteria are present, an inflow section of allowing an ammoniumcontaining liquid to flow into the anaerobic ammonium oxidation tank114, a discharge section of discharging the liquid treated in theanaerobic ammonium oxidation tank 114, a nitrate storage tank 112 ofstoring a certain concentration of nitrate, a nitrate addition device ofadding nitrate to the anaerobic ammonium oxidation tank 114 from thenitrate storage tank 112, and a nitrate addition amount control deviceof controlling the amount of nitrate added.

An ammonium containing liquid flows into the anaerobic ammoniumoxidation tank 114 from an inflow pipe 116 forming the inflow section bydriving an inflow pump 117. The anaerobic ammonium oxidation tank 114 ispacked with entrapping immobilization pellets 124 in which heterotrophicdenitrifying bacteria and anaerobic ammonium oxidizing bacteria areentrapped to be immobilized, and the pellets are brought into contactwith the ammonium containing liquid flowing into the tank. In this case,it is preferable to provide a stirrer, an anaerobic gas blower, or thelike (omitted in FIG. 5), for example, in order to cause a flow of theentrapping immobilization pellets 124 in the anaerobic ammoniumoxidation tank 114 to bring the pellets into contact with the ammoniumcontaining liquid more efficiently.

In the anaerobic ammonium oxidation tank 114, it is preferable thatheterotrophic denitrifying bacteria be controlled to have cells 10 to1,000 times of cells that anaerobic ammonium oxidizing bacteria have. Bycontrolling the cell number ratio to the above, heterotrophicdenitrifying bacteria can be prevented from treatment of oxidizingnitrite to nitrate and from a competition for nitrite with anaerobicammonium oxidizing bacteria.

From the nitrate storage tank 112 provided above the anaerobic ammoniumoxidation tank 114, a nitrate addition pipe 120 as the nitrate additiondevice is extended to the upper end of the anaerobic ammonium oxidationtank 114, and a certain concentration of nitrate stored in the nitratestorage tank 112 is added to the anaerobic ammonium oxidation tank 114.Thus, in an anaerobic atmosphere, the added nitrate is reduced tonitrite by heterotrophic denitrifying bacteria, and ammonium in theammonium containing liquid and nitrite are simultaneously denitrified byanaerobic ammonium oxidizing bacteria and removed as nitrogen gas. Theliquid treated in the anaerobic ammonium oxidation tank 114 isdischarged through a discharge pipe 118 forming the discharge section tooutside the system. A screen 126 is provided on the side of thedischarge section of the anaerobic ammonium oxidation tank 114, andprevents the entrapping immobilization pellets 124 from being dischargedtogether with the treated liquid. By storing a certain concentration ofnitrate in the nitrate storage tank 112, and adding nitrate to theanaerobic ammonium oxidation tank 114 from the nitrate storage tank 112in an amount corresponding to the necessary amount of nitrate in thismanner, an ammonium containing liquid can be treated constantly stably,and thus a treated liquid can be provided with high quality constantlystably.

The nitrate addition pipe 120 is provided with a nitrate valve 122 as adevice for controlling the amount of nitrate added. A certainconcentration of nitrate is added to anaerobic ammonium oxidation tank114 from the nitrate storage tank 112 in an amount controlled by openingand closing the nitrate valve 122. Nitrate is added to the anaerobicammonium oxidation tank 114 in an amount corresponding to the amount ofnitrate necessary for treating ammonium in an ammonium containingliquid. The necessary amount of nitrate is preferably an amount ofnitrate necessary for being reduced to nitrite by heterotrophicdenitrifying bacteria so that the amount of nitrite nitrogen in nitriteis 1 to 1.5 times the amount of ammonium nitrogen in ammonium.Specifically, in the anaerobic ammonium oxidation tank 114, the ratio ofthe amount of nitrite nitrogen (NO₂—N) in nitrite to the amount ofammonium nitrogen (NH₄—N) in ammonium contained in an ammoniumcontaining liquid to be treated has a close relation with the totalnitrogen removal ratio for the ammonium containing liquid (T-N removalratio). If the ratio between them is 1 to 1.5, the T-N removal ratio ishighest. If less than 1 or more than 1.5, the T-N removal ratio tends tobe drastically reduced.

FIG. 6 is a plan view showing a schematic configuration of equipment 130for treating an ammonium containing liquid according to a sixthembodiment of the present invention. The same member or device as intreatment equipment 110 according to the fifth embodiment shown in FIG.5 will be described with the same reference numeral, and the descriptionwill be omitted.

As shown in FIG. 6, in the treatment 130, an organic substance storagetank 132 is disposed in the anaerobic ammonium oxidation tank 114, inaddition to a nitrate storage tank 112.

The organic substance storage tank 132 has a structure that can store asolution of an organic substance in a solvent (typically water) with acertain concentration of organic substance added, or a powder of anorganic substance controlled so that a certain concentration of anorganic substance is added. The organic substance used is preferablymethanol, molasses, acetic acid, or the like, but is not specificallylimited. The organic substance storage tank 132 has a structure in whichan appropriate necessary amount of an organic substance is added to theanaerobic ammonium oxidation tank 114 by various measurements andcontrols. In this case, the organic substance stored in the organicsubstance storage tank 132 is not limited to the above-describednaturally occurring substance or a chemically synthesized substance. Itis basically enough only if a certain concentration of an organicsubstance is stored in the organic substance storage tank 132 and stablyadded to the anaerobic ammonium oxidation tank 114.

Accordingly, in the treatment equipment 130, from the nitrate storagetank 112 provided above the anaerobic ammonium oxidation tank 114, acertain concentration of nitrate stored is added to the anaerobicammonium oxidation tank 114 through the nitrate addition pipe 120. Onthe other hand, from the organic substance storage tank 132, a certainconcentration of an organic substance stored is added to the anaerobicammonium oxidation tank 114 through an organic substance addition pipe134 as an organic substance addition device extended to the upper end ofthe anaerobic ammonium oxidation tank 114.

The organic substance addition pipe 134 is provided with an organicsubstance valve 136 as a device for controlling the amount of theorganic substance added. A certain concentration of the organicsubstance is added to the anaerobic ammonium oxidation tank 114 from theorganic substance storage tank 132 in an amount controlled by openingand closing the valve 136. The organic substance is added to theanaerobic ammonium oxidation tank 114 in an amount corresponding to theamount necessary for treating ammonium in an ammonium containing liquid.The necessary amount of the organic substance is preferably set so thatthe C/NO₃—N ratio of the organic substance concentration to the nitratenitrogen concentration in an ammonium containing liquid in the anaerobicammonium oxidation tank 114 is 0.5 to 2.5. Heterotrophic denitrifyingbacteria retained in pellets 124,124 . . . can reduce nitrate to nitriteusing an organic substance as a hydrogen donor in a stable manner bykeeping the aforementioned C/NO₃—N ratio in the anaerobic ammoniumoxidation tank 114, and thus a competition for nitrite between anaerobicammonium oxidizing bacteria and heterotrophic denitrifying bacteria canbe controlled in the anaerobic ammonium oxidation tank 114.

FIG. 7 is a plan view showing a schematic configuration of equipment 150for treating an ammonium containing liquid according to a seventhembodiment of the present invention. The same member or device as in thefifth and sixth embodiments will be described with the same referencenumeral, and the description will be omitted.

As shown in FIG. 7, a concentration measuring instrument 138 formeasuring the ammonium nitrogen concentration in an ammonium containingliquid is provided in the middle of an inflow pipe 116. The valuesmeasured in the concentration measuring instrument 138 are sent to aconcentration monitoring-type nitrate control unit 140. The ammoniumnitrogen concentration may be measured in the concentration measuringinstrument 138 continuously or intermittently. The nitrate control unit140 calculates the amount of nitrate added corresponding to the amountof nitrate necessary for being reduced by heterotrophic denitrifyingbacteria to produce nitrite in an amount necessary for anaerobicammonium oxidizing bacteria in an anaerobic ammonium oxidation tank 114,and controls the opening of a nitrate valve 122 based on the calculatedaddition amount. It is preferable to previously measure the relationbetween the amount of nitrate added and the valve opening, and input therelation in the nitrate control unit 140. This allows appropriatecontrol of the amount of nitrate added in accordance with the ammoniumconcentration in the ammonium containing liquid. Accordingly, theequipment 150 for treating an ammonium containing liquid according tothe seventh embodiment of the present invention is effective when theammonium concentration in an ammonium containing liquid varies.

When the volume of the ammonium containing liquid flowing into theanaerobic ammonium oxidation tank 114 also varies, it is preferable toprovide, in the inflow pipe 116, an inflow volume measuring instrumentnot shown in FIG. 7 for measuring the inflow volume, in addition to theconcentration measuring instrument 138, to control the amount of nitrateadded with reference to the concentration and the inflow volume.

FIG. 8 is a plan view showing a schematic configuration of equipment 160for treating an ammonium containing liquid according to an eighthembodiment of the present invention, and shows a manner of controllingthe amount of nitrate added and the amount of an organic substance addedwith reference to the ammonium nitrogen concentration. The same memberor device as in the fifth to seventh embodiments will be described withthe same reference numeral, and the description will be omitted.

As shown in FIG. 8, in the treatment equipment 160, the concentration ofammonium nitrogen contained in an ammonium containing liquid flowinginto an anaerobic ammonium oxidation tank 114 is measured by aconcentration measuring instrument 138, and the measurement values aresent to a concentration monitoring-type control unit 142. Based on thesent measurement values, the control unit 142 calculates the amount ofnitrate added corresponding to the amount of nitrate necessary for beingreduced by heterotrophic denitrifying bacteria to produce nitrite in anamount necessary for anaerobic ammonium oxidizing bacteria in ananaerobic ammonium oxidation tank 114, and calculates the amount of anorganic substance necessary for attaining a C/NO₃—N ratio of 0.5 to 2.5which is a ratio of the organic carbon concentration to the nitratenitrogen concentration in an ammonium containing liquid in the anaerobicammonium oxidation tank 114. Then, the control unit 142 controls theopening and closing of a nitrate valve 122 and an organic substancevalve 136 based on the calculated amounts of nitrite and organicsubstance added, and regulates the amounts of nitrite and organicsubstance added. Consequently, nitrate reduction treatment byheterotrophic denitrifying bacteria and simultaneous denitrification ofnitrite and ammonium by anaerobic ammonium oxidizing bacteria can beappropriately carried out according to the ammonium concentration in anammonium containing liquid in the anaerobic ammonium oxidation tank 114.For this reason, the equipment is particularly effective when theammonium concentration in an ammonium containing liquid varies.

FIG. 9 is a plan view showing a schematic configuration of equipment 170for treating an ammonium containing liquid according to a ninthembodiment of the present invention. The same member or device as in thefifth to eighth embodiments will be described with the same referencenumeral, and the description will be omitted.

As shown in FIG. 9, an inflow volume measuring instrument 144 formeasuring the inflow volume of an ammonium containing liquid is providedin the middle of an inflow pipe 116. The values measured in the inflowvolume measuring instrument 144 are sent to an inflow volumemonitoring-type control unit 146. The inflow volume of the ammoniumcontaining liquid may be measured in the inflow volume measuringinstrument 144 continuously or intermittently. The control unit 146controls the opening and closing of a nitrate valve 122 to increase anddecrease the amount of nitrate added corresponding to the amount ofnitrate necessary for producing nitrite by heterotrophic denitrifyingbacteria in an amount corresponding to the necessary amount of nitritein direct proportion to an increase or decrease in the inflow volumemeasured in the inflow volume measuring instrument 144. At the sametime, the control unit 146 controls the opening and closing of anorganic substance valve 136 to increase and decrease the amount of anorganic substance added corresponding to the amount of the organicsubstance necessary for attaining a C/NO₃—N ratio of 0.5 to 2.5 which isa ratio of the organic carbon concentration to the nitrate nitrogenconcentration in an ammonium containing liquid in an anaerobic ammoniumoxidation tank 114. It is preferable to previously determine thenecessary amount of nitrate and the necessary amount of the organicsubstance by analyzing the ammonium nitrogen concentration in theammonium containing liquid.

Because of this, the treatment equipment 170 according to the ninthembodiment is effective when an ammonium containing liquid has a certainammonium concentration as in development wastewater. When the amount ofan organic substance is constant in an inflow ammonium containingliquid, and it is not necessary to control the organic substance in theanaerobic ammonium oxidation tank 114, the control unit 146 may controlonly the amount of nitrate added from the inflow volume.

FIG. 10 is a plan view showing a schematic configuration of equipment180 for treating an ammonium containing liquid according to a tenthembodiment of the present invention. The same apparatus, member, ordevice as in the fifth to ninth embodiments will be described with thesame reference numeral, and the description will be omitted.

As shown in FIG. 10, an anaerobic ammonium oxidation tank 114 is formedas a closed tank. In an upper space in the anaerobic ammonium oxidationtank 114, a trap 148 is formed, in which nitrogen gas produced byreaction of ammonium with nitrite in the anaerobic ammonium oxidationtank 114 is pooled. A gas recovery pipe 152 for recovering nitrogen gaspooled in the trap 148 is connected to an upper board 114A of theanaerobic ammonium oxidation tank 114. It is preferable to provide aliquid seal mechanism not shown in the figure to prevent nitrogen gasgenerated in the anaerobic ammonium oxidation tank 114 from being leakedtogether with the treated liquid in a connection section in which adischarge pipe 118 is connected to the anaerobic ammonium oxidation tank114. As the liquid seal mechanism, a known mechanism such as a liquidseal U-tube may be used.

In the middle of the gas recovery pipe 152, a gas production ratemeasuring instrument 154 is provided, in which the amount of gas flowingin the gas recovery pipe 152 is sequentially measured to determine theproduction rate (L/min) of nitrogen gas generated in the anaerobicammonium oxidation tank 114. Although gas recovered in the gas recoverypipe 152 may contain an air component brought from an ammoniumcontaining liquid, such a component is ignored because the gas containsthe component in an extremely small amount. Here, the gas productionrate refers to a nitrogen gas production rate. As the gas productionrate measuring instrument 154, a vortex flowmeter, float flowmeter, orintegrating flowmeter may be preferably used, for example.

The values measured in the gas production rate measuring instrument 154are sequentially input into a nitrogen gas monitoring-type control unit156. The control unit 156 increases or decreases the amount of nitrateadded, and monitors an increase or decrease in the nitrogen gasproduction rate Vn (L/min) measured in the gas production rate measuringinstrument 154 when the amount is increased or decreased, so that anamount of nitrate added and an amount of an organic substance addedwhich do not allow the gas production rate Vn to be increased ordecreased in proportion to an increase or decrease in the amount ofnitrate added and the amount of the organic substance added is definedas the necessary amount of nitrate and the necessary amount of theorganic substance. The amount of nitrate added is controlled bycontrolling the opening and closing of a nitrate valve 122 and anorganic substance valve 136.

In the treatment equipment 180, a certain concentration of an organicsubstance stored in an organic substance storage tank 132 is added tothe anaerobic ammonium oxidation tank 114 at the same time. Here, whenthe opening and closing of the organic substance valve 136 is controlledto attain a C/NO₃—N ratio of 0.5 to 2.5 which is a ratio of the organiccarbon concentration to the nitrate nitrogen concentration in anammonium containing liquid, the amount of the organic substance added iscontrolled to be the necessary amount.

For example, as shown in the flow chart of FIG. 11, in a nitrate controlprogram by nitrogen gas generation monitoring, the nitrogen gasproduction rate with respect to the amount of nitrate added at theinitial stage of operation of the treatment equipment 180 is measured,and the amount of nitrate added at the time of this gas production rateVn is used as the reference addition amount (step S10).

Next, the control unit 156 widens the opening of the nitrate valve 122in the step S12 to increase the amount of nitrate added to the anaerobicammonium oxidation tank 114 from a nitrate storage tank 112 by 3% (wt %or vol %) with respect to the reference addition amount. The controlunit 156 increases the amount of nitrate added by 3% in the step S14 tomonitor whether or not the gas production rate Vn measured in the gasproduction rate measuring instrument 154 is increased. When the gasproduction rate Vn is increased (by 3%, for example) in directproportion to an increase in the amount of nitrate added, the amount ofnitrate added may be insufficient, and thus the step S12 is repeated toincrease the amount of nitrate added by further 3% with respect to thereference addition amount.

When the gas production rate Vn is not increased in direct proportion toan increase in the amount of nitrate added, the amount of nitrate addedis excessive, and anaerobic ammonium oxidizing bacteria may have reducedactivity. Thus, the opening of the nitrate valve 122 and the organicsubstance valve 136 is narrowed in the step S16 to decrease the amountsof nitrate and organic substance added by 3%. The control unit 156decreases the amounts of nitrate and organic substance added by 3% tomonitor in the step S18 whether or not the gas production rate Vnmeasured in the gas production rate measuring instrument 154 isdecreased. When the gas production rate Vn is decreased (by 3%, forexample) in direct proportion to a decrease in the amounts of nitrateand organic substance added, the step S12 is repeated. When the gasproduction rate Vn is not decreased, nitrate and the organic substancemay still be excessive, and thus the step S16 is repeated.

Operations of the steps S12 to S18 are repeated in this manner to findan amount of nitrate added which does neither increase nor decrease thegas production rate. With reference to such an amount as the necessaryamount of nitrate, the amount of nitrate added is controlled. Thisallows the amount of nitrate added to be appropriately controlled, evenif the ammonium nitrogen concentration in the ammonium containing liquidor the inflow volume of the liquid is not measured, and furthermoreallows the amount of nitrate added to be controlled concurrently with anincrease or decrease in the treatment load such as an increase ordecrease in the ammonium concentration or an increase or decrease in theinflow volume. In the above-described program, the amount of nitrateadded is increased or decreased by 3%, but the amount is preferablyincreased or decreased by 2 to 5% as a percentage appropriatelyselected. This is because an increase or decrease in the gas productionrate cannot be accurately monitored in the steps S14 and S18 if theamount is increased or decreased by less than 2%, and the nitrateconcentration in the anaerobic ammonium oxidation tank 114 may bedrastically increased if the amount is increased or decreased by morethan 5%. When the step S12 or the step S14 is repeated, nitrate may beincreased or decreased by, for example, 2% instead of 3% as a nextcycle.

FIG. 12 is a plan view showing a schematic configuration of equipment190 for treating an ammonium containing liquid according to an eleventhembodiment of the present invention. The same apparatus, member, ordevice as in the fifth to tenth embodiments will be described with thesame reference numeral, and the description will be omitted.

As shown in FIG. 12, the treatment equipment 190 is mainly constitutedby an ammonium containing liquid storage tank 162 for storing anammonium containing liquid, a nitrate storage tank 112 for storing acertain concentration of nitrate, an organic substance storage tank 132for storing a certain concentration of an organic substance, verticalanaerobic ammonium oxidation tanks 114 having a removable cartridgestructure, and a treated liquid storage tank 164 for storing the liquidtreated in the anaerobic ammonium oxidation tanks 114. Thecartridge-type anaerobic ammonium oxidation tanks 114 are preferablyclosed cylinder vessels packed with entrapping immobilization pellets asfixed beds.

An inflow pipe 116 that allows an ammonium containing liquid in theammonium containing liquid storage tank 162 to flow into the anaerobicammonium oxidation tanks 114 has two branches on the top (on the side ofthe anaerobic ammonium oxidation tanks). Valves 122 are provided in themiddle of the two branched pipes 116A, 116A, and male parts of one-touchconnectors 166 are provided on the tops of the two pipes 116A, 116A. Anitrate addition pipe 120 of adding nitrate in the nitrate storage tank112 to the anaerobic ammonium oxidation tank 114 has a plurality ofbranched pipes 120A, 120A equipped with the valves 122. Nitrate additionpumps 168 are provided in the pipes 120A, and male parts of theone-touch connectors 166 are provided on each of the tops of the pipes120A, 120A. Similarly, an organic substance addition pipe 134 of addingan organic substance in the organic substance storage tank 132 to theanaerobic ammonium oxidation tank 114 has a plurality of branched pipes134A, 134A equipped with the valves 122. Organic substance additionpumps 172 are provided in the pipes 134A, and male parts of theone-touch connectors 166 are provided on each of the tops of the pipes134A, 134A. Further, a discharge pipe 118 for water treated in theanaerobic ammonium oxidation tanks 114 has two branches on the top (onthe side of the anaerobic ammonium oxidation tanks), and male parts ofthe one-touch connectors 166 are provided on the tops of the two pipes118A, 118A equipped with valves.

On the other hand, connection pipes 174, 174 . . . are respectivelyprovided on the lower ends, the upper ends, and the lateral sides of theanaerobic ammonium oxidation tanks 114, and female parts of theone-touch connectors 166 are provided on the tops of the respectiveconnection pipes 174. Thus, the two anaerobic ammonium oxidation tanks114 can be removably attached to the inflow pipe 116, the discharge pipe118, the nitrate addition pipe 120, and the organic substance additionpipe 134 through the one-touch connectors 166.

The treatment equipment according to the present embodiment isconstituted by two anaerobic ammonium oxidation tanks 114 that can beremoved. However, the number of the anaerobic ammonium oxidation tanks14 may be one or more, and the inflow pipe 116, the discharge pipe 118,the nitrate addition pipe 120, and the organic substance addition pipe134 may be formed with one or more branches corresponding to the numberof the tanks.

In the treatment equipment 190 thus constituted according to theeleventh embodiment, a plurality of the anaerobic ammonium oxidationtanks 114 can be used by rotation. Further, it is convenient if one ofthe multiple anaerobic ammonium oxidation tanks 114 is used as areserved anaerobic ammonium oxidation tank 114 when anaerobic ammoniumoxidizing bacteria are killed or have reduced activity in the anaerobicammonium oxidation tanks 114 in use. Accordingly, the treatmentequipment 190 according to the eleventh aspect of the present inventionshown in FIG. 12 is effective when treating a small-scale waste liquidcontaining a certain concentration of ammonium such as a developmentwaste liquid.

[3] Next, embodiments of a process of supplying nitrate to an anaerobicammonium oxidation tank from a nitrification tank will be described withreference to FIGS. 13 to 22.

FIG. 13 shows equipment 210 for treating an ammonium containing liquidaccording to a twelfth embodiment. The equipment is constituted by anitrification tank 212 in an aerobic atmosphere in which nitrifyingbacteria are present; an anaerobic ammonium oxidation tank 214 in ananaerobic atmosphere in which heterotrophic denitrifying bacteria andanaerobic ammonium oxidizing bacteria are present; an inflow pipe 220 ofallowing an ammonium containing liquid to flow into the nitrificationtank 212 and the anaerobic ammonium oxidation tank 214; a nitrifiedliquid pipe 222 of allowing the nitrified liquid treated in thenitrification tank 212 to flow into the anaerobic ammonium oxidationtank 214; and a discharge pipe 224 of discharging the liquid treated inthe anaerobic ammonium oxidation tank 214.

Here, the content, type, culturing method, and maintenance form ofvarious bacteria such as heterotrophic denitrifying bacteria andanaerobic ammonium oxidizing bacteria, and the form of variousentrapping immobilization pellets may be the same as described above ineach embodiment. The anaerobic ammonium oxidation tank 214 used here maybe the same as the above-described anaerobic ammonium oxidation tank114.

An ammonium containing liquid flows into the nitrification tank 212 froman inflow pipe 220 forming the inflow section by driving an inflow pump(not shown). The nitrification tank 212 is packed with filter media towhich nitrifying bacteria are attached (not shown), and the filter mediaare brought into contact with the inflow ammonium containing liquid.

The nitrified liquid pipe 222 allows the nitrified liquid treated in thenitrification tank 212 to flow into the anaerobic ammonium oxidationtank 214.

An ammonium containing liquid flows into the anaerobic ammoniumoxidation tank 214 from the inflow pipe 220 forming the inflow sectionby driving an inflow pump (not shown). Further, the nitrified liquidflows into the tank 214 from the nitrified liquid pipe 222.

The nitrified liquid pipe 222 is extended from the nitrification tank212 to the anaerobic ammonium oxidation tank 214. A certainconcentration of nitrate nitrified in the nitrification tank 212 isadded to the anaerobic ammonium oxidation tank 214. Thus, in ananaerobic atmosphere, nitrate added from the nitrification tank 212 isreduced to nitrite by heterotrophic denitrifying bacteria, and ammoniumin the ammonium containing liquid and nitrite are simultaneouslydenitrified by anaerobic ammonium oxidizing bacteria and removed asnitrogen gas. The necessary amount of nitrate and the like are the sameas in the aforementioned fifth to eleventh embodiments.

The liquid treated in the anaerobic ammonium oxidation tank 214 isdischarged through the discharge pipe 224 forming the discharge sectionto outside the system. A screen 218 is provided on the side of thedischarge section of the anaerobic ammonium oxidation tank 214, andprevents entrapping immobilization pellets 216 from being dischargedtogether with the treated liquid. In this manner, an ammonium containingliquid can be treated constantly stably by supplying a certainconcentration of nitrate to the anaerobic ammonium oxidation tank 214from the nitrification tank 212, and thus a treated liquid can beprovided with good quality constantly stably.

FIG. 14 is a plan view showing a schematic configuration of equipment230 for treating an ammonium containing liquid according to a thirteenthembodiment of the present invention.

As shown in FIG. 14, in the treatment equipment 230, a nitrificationtank 212 is placed downstream of an anaerobic ammonium oxidation tank214. Ammonium is nitrified in the downstream nitrification tank 212, theproduced nitrate is fed back to the anaerobic ammonium oxidation tank214 through a feedback pipe 232, and nitrate and ammonium aredenitrified in the anaerobic ammonium oxidation tank 214. The treatmentequipment 230 are effective in low-concentration ammonium treatment suchas sewage treatment.

FIGS. 15 and 16 are plan views showing schematic configurations ofequipments 240 and 250 for treating an ammonium containing liquidaccording to fourteenth and fifteenth embodiments of the presentinvention.

As shown in FIG. 15, in the treatment equipment 240, a denitrificationtank 226 is placed upstream of an anaerobic ammonium oxidation tank 214in the treatment equipment 210 of FIG. 13. In the treatment equipment250 of FIG. 16, as in the equipment of FIG. 15, a denitrification tank226 is placed upstream of an anaerobic ammonium oxidation tank 214 inthe treatment equipment 230 of FIG. 14.

In the denitrification tank 226, nitrate in the treated liquid from thenitrification tank 212 is denitrified to N₂ gas by denitrifying bacteriaby use of an organic substance contained in an ammonium containingliquid.

If the denitrification tank 226 is placed upstream of the anaerobicammonium oxidation tank 214 in this manner, an organic component can beremoved when denitrifying nitrate. In this case, if the organiccomponent is completely removed, reduction from nitrate does not proceedin the anaerobic ammonium oxidation tank 214. Thus, the C/NO₃—N ratio ofthe organic substance concentration to the nitrate nitrogenconcentration in an ammonium containing liquid in the anaerobic ammoniumoxidation tank 214 is preferably 0.5 to 2.5. These treatment equipments240 and 250 are effective when wastewater has a high organic substanceconcentration and an organic substance inhibits ammonium oxidationreaction.

FIG. 17 is a plan view showing a schematic configuration of equipment260 for treating an ammonium containing liquid according to a sixteenthembodiment of the present invention.

As shown in FIG. 17, in the treatment equipment 260, an organicsubstance storage tank 242 is connected to an anaerobic ammoniumoxidation tank 214 in the treatment equipment 210 of FIG. 13 through anorganic substance addition pipe 244. If wastewater lacks an organiccomponent, an organic substance can be supplied. The opening and closingof an organic substance valve (not shown) is controlled to increase anddecrease the amount of an organic substance added corresponding to theamount of the organic substance necessary for attaining a C/NO₃—N ratioof 0.5 to 2.5 which is a ratio of the organic carbon concentration tothe nitrate nitrogen concentration in an ammonium containing liquid inthe anaerobic ammonium oxidation tank 214. It is preferable topreviously determine the necessary amount of nitrate and the necessaryamount of the organic substance by analyzing the ammonium nitrogenconcentration in the ammonium containing liquid. An organic substancestorage tank 242 can also be placed in the anaerobic ammonium oxidationtanks 214 in the treatment equipments of FIGS. 13 to 16.

FIG. 18 is a plan view showing a schematic configuration of equipment270 for treating an ammonium containing liquid according to aseventeenth embodiment of the present invention.

As shown in FIG. 18, in the present embodiment, an organic substancestorage tank 242 is provided in an anaerobic ammonium oxidation tank 214in the treatment equipment 210 of FIG. 13, and a nitrification tank 212of the equipment 210 is provided as multiple tanks.

Nitrifying bacteria in the nitrification tanks 212, 212 . . . arepreferably immobilized in or to an immobilization material to formnitrification sludge pellets 215. The opening and closing of an organicsubstance valve (not shown) is controlled to increase and decrease theamount of an organic substance added corresponding to the amount of theorganic substance necessary for attaining a C/NO₃—N ratio of 0.5 to 2.5which is a ratio of the organic carbon concentration to the nitratenitrogen concentration in an ammonium containing liquid in the anaerobicammonium oxidation tank 214 as described above. It is preferable topreviously determine the necessary amount of nitrate and the necessaryamount of the organic substance by analyzing the ammonium nitrogenconcentration in the ammonium containing liquid. The treatment equipment270 is effective when treating high-concentration ammonium wastewaterhaving an ammonium nitrogen concentration of 500 mg/L or more.

FIG. 19 is a plan view showing a schematic configuration of equipment280 for treating an ammonium containing liquid according to aneighteenth embodiment of the present invention.

As shown in FIG. 19, in the present embodiment, an anaerobic ammoniumoxidation tank 214 in the treatment equipment 270 of FIG. 18 is providedas multiple tanks, and a nitrified liquid pipe 222 and an organicsubstance addition pipe 244 are connected to the anaerobic ammoniumoxidation tanks 214, 214 . . . , respectively. The opening and closingof an organic substance valve (not shown) is controlled to increase anddecrease the amount of an organic substance added corresponding to theamount of the organic substance necessary for attaining a C/NO₃—N ratioof 0.5 to 2.5 which is a ratio of the organic carbon concentration tothe nitrate nitrogen concentration in an ammonium containing liquid inthe anaerobic ammonium oxidation tank 214. It is preferable topreviously determine the necessary amount of nitrate and the necessaryamount of the organic substance by analyzing the ammonium nitrogenconcentration in the ammonium containing liquid. In this manner, theammonium removal ratio is improved by supplying a nitrified liquid andan organic substance to the anaerobic ammonium oxidation tanks 214, 214. . .

FIG. 20 is a plan view showing a schematic configuration of equipment290 for treating an ammonium containing liquid according to a nineteenthembodiment of the present invention.

As shown in FIG. 20, in the treatment equipment 290, a settlement tank252 is placed downstream of a nitrification tank 212 in the treatmentequipment 230 of FIG. 14. This is a case where feedback sludge is usedas a nitrified liquid. In the case of treatment of low-concentrationnitrogen wastewater such as sewage treatment, it is preferable that thewastewater be fed back to an anaerobic ammonium oxidation tank 214through a sludge feedback pipe 254 at a feedback ratio of 50 to 100%.

FIG. 21 is a plan view showing a schematic configuration of equipment300 for treating an ammonium containing liquid according to a twentiethembodiment of the present invention.

As shown in FIG. 21, in the treatment equipment 300, a settlement tank252 is placed downstream of a nitrification tank 212 in the treatmentequipment 250 of FIG. 16. This is a case where feedback sludge is usedas a nitrified liquid, as in the treatment equipment 290. In the case oftreatment of low-concentration nitrogen wastewater such as sewagetreatment, it is preferable that the wastewater be fed back to ananaerobic ammonium oxidation tank 214 through a sludge feedback pipe 254at a feedback ratio of 50 to 100%.

FIG. 22 is a plan view showing a schematic configuration of equipment310 for treating an ammonium containing liquid according to atwenty-first embodiment of the present invention.

As shown in FIG. 22, the nitrified liquid pipe 222 is provided in thetreatment equipment 310, so that the nitrified liquid in the mostupstream of nitrification tanks 212, 212 . . . of the treatmentequipment 280 can be supplied to anaerobic ammonium oxidation tanks 214.The first nitrification tank 212 easily produces nitrite. Thus, bysetting the tank in this manner, the amount of an organic substanceadded can be saved. When nitrite is produced in the second nitrificationtank 212, the amount of the organic substance added can be further savedby providing the nitrified liquid pipe 222 so that the nitrified liquidcan also be supplied to the anaerobic ammonium oxidation tanks 214.

The first to twenty-first embodiments of the present invention are asdescribed above. However, the present invention is not limited to theabove embodiments, and various embodiments are possible.

For examples, in the aforementioned treatment equipments according tothe present embodiments shown in FIGS. 3A to 3D, FIGS. 5 to 10, andFIGS. 13 to 22, the number, shape, material, and the like of eachapparatus and member used are not specifically limited.

The embodiments shown in FIGS. 5 to 10 and FIGS. 13 to 22 are describedwith the proviso that heterotrophic denitrifying bacteria and anaerobicammonium oxidizing bacteria in the anaerobic ammonium oxidation tanks114 and 214 are maintained in the form of entrapping immobilizationpellets. However, there are no specific limitations to the maintenanceform. Any of floating bacteria, a biofilm, and attachment immobilizationpellets are possible.

The first to fourth embodiments shown in FIGS. 3A to 3D, the fifth toeleventh embodiments shown in FIGS. 5 to 12, and the twelfth totwenty-first embodiments shown in FIGS. 13 to 22 are individuallydescribed. However, the present embodiments are not limited thereto. Forexample, an embodiment of a combination of any one or more from any oneof the first to fourth embodiments, any one of the fifth to eleventhembodiments, and any one of the twelfth to twenty-first embodiments ispossible.

EXAMPLES

Example 1, Example 2, and Example 3 of the present invention will bedescribed below based on the above description. However, the presentinvention is not limited to these Examples.

Example 1 Example 1-1

First, in this Example, a treatment test for synthetic wastewatercontaining ammonium, nitrate, and sodium acetate was carried out inequipments 10 and 20 for treating an ammonium containing liquid shown inFIGS. 3A and 3B, and a treatment test for synthetic wastewatercontaining ammonium and sodium acetate was carried out in equipments 30and 40 for treating an ammonium containing liquid shown in FIGS. 3C and3D, under the conditions of the following Tests 1 to 6 and Test 7 asComparative Example using a conventional process, respectively.

In the treatment equipments 10 and 20, synthetic wastewater having aratio of the ammonium nitrogen concentration to the nitrateconcentration of 1:1, having T/N controlled to 80 mg/L, and containingsodium acetate as an organic source added to attain a C/NO₃—N ratio asdescribed above of 1 was used for the Tests. In the treatment equipments30 and 40, synthetic wastewater having an ammonium nitrogenconcentration of 80 mg/L and containing sodium acetate as an organicsource added to correlate with the amount of nitrate produced in anitrification tank 24 and attain a C/NO₃—N ratio of 1 was used. Also inthe conventional process, this synthetic wastewater was used. Theequipments 10, 20, 30, and 40 for treating an ammonium containing liquidwere operated at a nitrogen load of 1.6 kg-N/m³/day. Detailed conditionsare as shown below.

(Test 1)

The equipment 10 for treating an ammonium containing liquid shown inFIG. 3A was used.

Nitrate reduction tank 12 (anaerobic tank): Retention time 32 minutes,tank packed with nonwoven cloth packing material at 30%, denitrifyingbacteria introduced at 6×10⁷ cells/mL, components in tank stirred at 60rpm

Anaerobic ammonium oxidation tank 14: Retention time 40 minutes, tankpacked with nonwoven cloth packing material at 30%, anaerobic ammoniumoxidizing bacteria introduced at 4×10⁵ cells/mL, components in tankstirred at 60 rpm

(Test 2)

The equipment 20 for treating an ammonium containing liquid shown inFIG. 3B was used.

Anaerobic ammonium oxidation tank 14: Retention time 72 minutes, tankpacked with nonwoven cloth packing material at 30%, heterotrophicdenitrifying bacteria introduced at 6×10⁷ cells/mL, anaerobic ammoniumoxidizing bacteria introduced at 4×10⁵ cells/mL, components in tankstirred at 60 rpm

(Test 3)

The equipment 20 for treating an ammonium containing liquid shown inFIG. 3B was used.

Anaerobic ammonium oxidation tank 14: Retention time 72 minutes, tankpacked with entrapping immobilization pellets 50A and 50B shown in FIG.4A at 20% (10% for pellets 50A in which 6×10⁸ cells/mL of heterotrophicdenitrifying bacteria are entrapped to be immobilized; 10% for pellets50B in which 4×10⁶ cells/mL of anaerobic ammonium oxidation bacteria areentrapped to be immobilized), components in tank stirred at 60 rpm

(Test 4)

The equipment 20 for treating an ammonium containing liquid shown inFIG. 3B was used.

-   -   Anaerobic ammonium oxidation tank 14: Retention time 72 minutes,        tank packed with entrapping immobilization pellets 50 shown in        FIG. 4B        -   (pellets in which 3×10⁸ cells/mL of heterotrophic            denitrifying bacteria and 2×10⁶ cells/mL of anaerobic            ammonium oxidizing bacteria are entrapped to be immobilized)            at 20%, components in tank stirred at 60 rpm

(Test 5)

The equipment 20 for treating an ammonium containing liquid shown inFIG. 3B was used.

Anaerobic ammonium oxidation tank 14: Retention time 72 minutes, tankpacked with entrapping immobilization pellets 50′ shown in FIG. 4C(pellets in which 3×10⁸ cells/mL of heterotrophic denitrifying bacteriaare entrapped to be immobilized near the surface, and 2×10⁶ cells/mL ofanaerobic ammonium oxidizing bacteria are entrapped to be immobilized atthe center) at 20%, components in tank stirred at 60 rpm

(Test 6)

The equipment 30 for treating an ammonium containing liquid shown inFIG. 3C was used.

Anaerobic tank 22: Retention time 40 minutes, tank packed withentrapping immobilization pellets 50′ shown in FIG. 4C (pellets in which3×10⁸ cells/mL of heterotrophic denitrifying bacteria are entrapped tobe immobilized near the surface, and 2×10⁶ cells/mL of anaerobicammonium oxidizing bacteria are entrapped to be immobilized at thecenter) at 20%, components in tank stirred at 60 rpm

Aerobic tank 24: Retention time 32 minutes, tank packed with nonwovencloth packing material at 30%, activated sludge introduced at 2,000 mg/Land attached to nonwoven cloth, tank aerated by aeration unit 26 whilemaintaining dissolved oxygen at 3 mg/L or more 100% circulation throughcirculation line 28

(Test 7)

Comparative Example in which the same tank configuration as in theequipment 30 for treating an ammonium containing liquid shown in FIG. 3Cwas employed, but heterotrophic denitrifying bacteria were neitherintroduced into the tank nor added to pellets.

Anaerobic tank 22: Retention time 40 minutes, tank packed with nonwovencloth packing material at 30%, activated sludge introduced at 2,000mg/mL and attached to nonwoven cloth, components in tank stirred at 60rpm

Aerobic tank 24: Retention time 32 minutes, tank packed with nonwovencloth packing material at 30%, activated sludge introduced at 2,000 mg/Land attached to nonwoven cloth, tank aerated by aeration unit 26 whilemaintaining dissolved oxygen at 3 mg/L or more

100% circulation through circulation line 28

Treatment operations were carried out in the Tests described above. Onemonth after completion of acclimatization, the treatment was madestable, and the nitrogen removal ratio at that time was examined. Theresults are shown in the following Table 2.

TABLE 2 T-N value in treated T-N removal ratio water (mg/L) (%) Test 136~42 48~55 Test 2 14~28 65~83 Test 3 12~24 70~85 Test 4  5~20 75~94Test 5  5~15 81~94 Test 6 10 or less 87 or more Test 7 52~70 13~35

According to Table 2, the nitrogen removal ratios attained in Tests 1 to6 were higher than that attained in Test 7 as Comparative Example.

Example 1-2

Next, in this Example, a treatment test for synthetic wastewatercontaining ammonium and sodium acetate was carried out in the equipment30 for treating an ammonium containing liquid shown in FIG. 3C under theconditions of the inventive process and the conventional process.

Synthetic wastewater having an ammonium nitrogen concentration of 40mg/L and containing sodium acetate as an organic source added to attaina C/NO₃—N ratio as described above of 1 was used for the Tests. Theequipment 30 for treating an ammonium containing liquid was operated ata nitrogen load of 0.6 kg-N/m³/day. Detailed conditions are as shownbelow.

(Test 1)

The equipment 30 for treating an ammonium containing liquid shown inFIG. 3C was used.

Anaerobic tank 22: Retention time 46 minutes, tank packed withentrapping immobilization pellets 50′ shown in FIG. 4C (pellets in which3×10⁸ cells/mL of heterotrophic denitrifying bacteria are entrapped tobe immobilized near the surface, and 2×10⁶ cells/mL of anaerobicammonium oxidizing bacteria are entrapped to be immobilized at thecenter) at 20%, components in tank stirred at 60 rpm

Aerobic tank 24: Retention time 50 minutes, tank packed with nonwovencloth packing material at 30%, activated sludge introduced at 2,000 mg/Land attached to nonwoven cloth, tank aerated by aeration unit 26 whilemaintaining dissolved oxygen at 3 mg/L or more

100% circulation through circulation line 28

(Test 2)

Comparative Example in which the same tank configuration as in theequipment 30 for treating an ammonium containing liquid shown in FIG. 3Cwas employed, but heterotrophic denitrifying bacteria were neitherintroduced into the tank nor added to pellets.

Anaerobic tank 22: Retention time 46 minutes, tank packed with nonwovencloth packing material at 30%, activated sludge introduced at 2,000mg/mL and attached to nonwoven cloth, components in tank stirred at 60rpm

Aerobic tank 24: Retention time 50 minutes, tank packed with nonwovencloth packing material at 30%, activated sludge introduced at 2,000 mg/Land attached to nonwoven cloth, tank aerated by aeration unit 26 whilemaintaining dissolved oxygen at 3 mg/L or more

100% circulation through circulation line 28

The same wastewater treatment operation was carried out in Tests 1 and 2described above. One month after completion of acclimatization, thetreatment was made stable, and the T-N value in the treated water wasmeasured at that time.

The results show that the T-N value in the treated water was 10 mg/L orless in Test 1, but the T-N value in the treated water was 25 to 30 mg/Lin Test 2 as a Comparative Example.

As described in the above Examples 1-1 and 1-2, when the presentinvention is employed, anaerobic ammonium oxidation can be carried outusing nitrate which can be supplied in a more stable manner.Accordingly, a process and equipment for treating an ammonium containingliquid can be provided which can carry out high-speed denitrificationstably if the nitrogen components in the ammonium containing liquidvary.

Example 2 Example 2-1

In this treatment, an ammonium containing liquid was treated usingtreatment equipment 110 shown in FIG. 5. The composition and the like ofentrapping immobilization pellets with which an anaerobic ammoniumoxidation tank 114 was filled are as shown in Table 3.

TABLE 3 Composition ratio Composition component (weight %) Accumulatedsludge Containing 2 × 10⁶ cells/mL of 50 concentrate of heterotrophicnitrifying heterotrophic bacteria and nitrifying bacteria and 2 × 10⁵cells/mL of anaerobic anaerobic ammonium ammonium oxidizing bacteriaoxidizing bacteria Polyethylene glycol diacrylate 4 Acrylamide 1N,N,N′,N′-tetramethylethylenediamine 0.5 Potassium persulfate 0.25 Water44.25

After mixing the above-described components, the above composition wasgelled by addition of potassium persulfate, and the gel was formed into3 mm×3 mm squares to prepare entrapping immobilization pellets 124.

(Test Conditions for Treatment Equipment)

-   -   Ammonium containing liquid: Industrial wastewater having an        ammonium nitrogen (NH₄—N) concentration of 90 to 120 mg/L and a        BOD concentration of 90 to 130 mg/L

Amount of nitrate added: A certain amount of nitrate with a nitratenitrogen (NO₃—N) concentration of 150 mg/L

Retention time in anaerobic ammonium oxidation tank 114: 2 hours

Packing ratio of entrapping immobilization pellets: 20%

Mechanical stirring in the anaerobic ammonium oxidation tank 114 causeda flow of pellets 124, 124 . . . .

After continuous treatment under the above-described conditions andacclimatization for one month, ammonium in the ammonium containingliquid and nitrite were anaerobically simultaneously denitrified in theanaerobic ammonium oxidation tank 114, and the treated liquid wasmaintained to have a total nitrogen concentration (T-N) of 30 to 50 mg/Lin a stable manner.

In the Example using the treatment equipment 110 of FIG. 5, industrialwastewater not containing a BOD component and having an ammoniumnitrogen (NH₄—N) concentration of 90 to 120 mg/L and NO₃—N concentrationof 120 to 180 mg/L was retained in the anaerobic ammonium oxidation tank114 for a retention time of 2 hours, and sodium acetate as an organicsubstance was added thereto with a C/NO₃—N ratio of 1.2, to carry outtreatment operation. As a result, continuous treatment was performed ina stable manner, and the treated liquid was maintained to have a totalnitrogen concentration (T-N) of 30 to 50 mg/L.

Example 2-2

In this Example, as Tests 1 to 3, an ammonium containing liquid wastreated with the same entrapping immobilization pellets as in Example2-1, using treatment equipment 160 in FIG. 8, treatment equipment 170 inFIG. 9, and treatment equipment 180 in FIG. 10. Treatment conditions inTests 1 to 3 are as follows.

(Test 1)

The treatment equipment 160 shown in FIG. 8 was used.

Ammonium containing liquid to be treated: Industrial wastewater havingan ammonium nitrogen (NH₄—N) concentration of 90 to 120 mg/L

Amount of nitrate added: Nitrate with a nitrate nitrogen (NO₃—N)concentration 1.8 times of the ammonium nitrogen (NH₄—N) concentrationadded by ammonium monitoring control

Amount of organic substance added: Molasses added at a C/NO₃—N ratio ofmolasses to nitrate nitrogen of 1.2 by ammonium monitoring control

Retention time in anaerobic ammonium oxidation tank 114: 2 hours

Amount of packed pellets in anaerobic ammonium oxidation tank 114: 20%

Mechanical stirring in the anaerobic ammonium oxidation tank 114 causeda flow of pellets 124, 124 . . . .

(Test 2)

The treatment equipment 170 shown in FIG. 9 was used.

Ammonium containing liquid to be treated: Industrial wastewater havingan ammonium nitrogen (NH₄—N) concentration of 90 to 120 mg/L

Amount of nitrate added: Nitrate with a nitrate nitrogen (NO₃—N)concentration 1.8 times of a predetermined average ammonium nitrogen(NH₄—N) concentration of 105 mg/L added by inflow volume control

Amount of organic substance added: Molasses added at a C/NO₃—N ratio ofmolasses to nitrate nitrogen of 1.2 by ammonium monitoring control

Retention time in anaerobic ammonium oxidation tank 114: 2 hours

Amount of packed pellets in anaerobic ammonium oxidation tank 114: 20%Mechanical stirring in the anaerobic ammonium oxidation tank 114 causeda flow of pellets 124, 124 . . . .

(Test 3)

The treatment equipment 180 shown in FIG. 10 was used.

Ammonium containing liquid to be treated: Industrial wastewater havingan ammonium nitrogen (NH₄—N) concentration of 90 to 120 mg/L

Amount of nitrate added: Nitrate with a nitrate nitrogen (NO₃—N)concentration 1.4 times of a predetermined average ammonium nitrogen(NH₄—N) concentration of 105 mg/L added by nitrogen gas productionamount control and then controlled in accordance with flow chart shownin FIG. 11

Amount of organic substance added: Molasses added at a C/NO₃—N ratio ofmolasses to nitrate nitrogen of 1.2

Retention time in anaerobic ammonium oxidation tank 114: 2 hours

Amount of packed pellets in anaerobic ammonium oxidation tank 114: 20%

Mechanical stirring in the anaerobic ammonium oxidation tank 114 causeda flow of pellets 124, 124 . . . .

The results of the above-described Tests 1 to 3 are shown in Table 4. InComparative Examples 1 and 2 in Table 4, treatment was carried outwithout addition of nitrate using the treatment equipment 130 shown inFIG. 6.

TABLE 4 Total nitrogen concentration in Treatment equipment treatedwater (mg/L) Test 1 FIG. 8 15~26 Test 2 FIG. 9 18~30 Test 3 FIG. 1010~22 Comparative Example 1 FIG. 6, nitrate not added  91~124Comparative Example 2 FIG. 6, methanol added  87~114 instead of nitrate

As is clear from Table 4, Tests 1 to 3 provided treated liquids with atotal nitrogen concentration of 10 to 30 mg/L each, and could treatammonium containing liquids in a stable manner.

On the contrary, Comparative Examples 1 and 2 provided treated liquidswith a total nitrogen concentration of 87 to 124 mg/L each, and couldnot treat ammonium in ammonium containing liquids almost at all.

Ammonium treatment by the conventional processes needs nitrificationreaction and denitrification reaction. The nitrification reaction needsa retention time of 4 to 6 hours, the denitrification reaction needs aretention time of 3 to 6 hours, and the treatment needs methanol in anamount three times greater than that of nitrogen. Accordingly, thetreatment needs large-scale treatment equipment.

On the contrary, treatment in Tests 1 to 3 simply involves adding anecessary amount of nitrate from the nitrate storage tank 112 and anecessary amount of an organic substance from an organic substancestorage tank 132 to the anaerobic ammonium oxidation tank 114, whilebringing an ammonium containing liquid into contact with heterotrophicdenitrifying bacteria and anaerobic ammonium oxidizing bacteria in ananaerobic atmosphere in the anaerobic ammonium oxidation tank 114.Consequently, the retention time can be shortened to one hour, and anammonium containing liquid can be treated constantly stably.Accordingly, the process of the present invention can reduce the size oftreatment equipment as compared with a conventional process requiring anitrification tank and a denitrification tank, can be operated at alower running cost, and is thus an extremely inexpensive treatmentprocess.

Example 2-3

In this treatment, an ammonium containing liquid was treated usingtreatment equipment 190 shown in FIG. 12. The composition and the likeof entrapping immobilization pellets with which anaerobic ammoniumoxidation tanks 114 were filled are the same as in the aforementionedTable 3. After mixing the components in Table 3 in the same manner asabove, the above composition was gelled by addition of potassiumpersulfate, and the gel was formed into 3 mm×3 mm squares to prepareentrapping immobilization pellets 124.

(Test Conditions for Treatment Equipment)

Ammonium containing liquid: Diluted development wastewater with anammonium nitrogen (NH₄—N) concentration of 2,000 mg/L

Amount of nitrate added: Nitrate containing nitrogen in an amount 1.5times of ammonium nitrogen (NH₄—N) continuously added

Amount of organic substance added: Methanol in an amount 0.8 time ofnitrate nitrogen (NO₃—N) continuously added

Retention time in anaerobic ammonium oxidation tanks 114: 4 hours

Packing ratio of entrapping immobilization pellets 124: 30%

Anaerobic mechanical stirring in the anaerobic ammonium oxidation tanks114 caused a flow of entrapping immobilization pellets.

As a result of continuous treatment under the above conditions, ammoniumin the ammonium containing liquid and nitrite produced by reduction ofnitrate added from a nitrate storage tank 112 by heterotrophicdenitrifying bacteria were simultaneously denitrified in the anaerobicammonium oxidation tanks 114, and the treated liquid was maintained tohave a total nitrogen concentration of 120 to 180 mg/L in a stablemanner.

In this manner, by employing the present invention, ammonium in anammonium containing liquid could be denitrified at a high speed.

Example 3 Example 3-1

In this treatment, an ammonium containing liquid was treated usingtreatment equipment 210 shown in FIG. 13.

The composition and the like of entrapping immobilization pellets 216with which an anaerobic ammonium oxidation tank 214 was filled are thesame as in the aforementioned Table 3.

After mixing the components in Table 3, the above composition was gelledby addition of potassium persulfate, and the gel was formed into 3 mm×3mm squares to prepare entrapping immobilization pellets 216.

(Test Conditions for Treatment Equipment)

Ammonium containing liquid: Industrial wastewater having an ammoniumnitrogen (NH₄—N) concentration of 90 to 120 mg/L and a BOD concentrationof 90 to 130 mg/L

Retention time in nitrification tank 212: 6 hours

Nitrification tank 212 packed with contact filter media

Retention time in anaerobic ammonium oxidation tanks 214: 2 hours

Packing ratio of entrapping immobilization pellets 216 in anaerobicammonium oxidation tank 214: 20%

Mechanical stirring in the anaerobic ammonium oxidation tank 214 causeda flow of entrapping immobilization pellets 216, 216 . . . .

After continuous treatment under the above-described conditions andacclimatization for one month, ammonium and nitrite were simultaneouslyremoved, and the treated liquid was maintained to have a total nitrogenconcentration (T-N) of 12 to 20 mg/L in a stable manner.

Example 3-2

In this Example using treatment equipment 230 of FIG. 14, an ammoniumcontaining liquid was treated with entrapping immobilization pellets 216in the same manner as in Example 3-1. The specification of anitrification tank 212 and an anaerobic ammonium oxidation tank 214 andthe wastewater used were the same as in Example 3-1. The equipment wasoperated at a nitrified liquid feedback ratio of 100%.

After continuous treatment under the above-described conditions andacclimatization for one month, ammonium and nitrite were simultaneouslyremoved, and the treated liquid was maintained to have a total nitrogenconcentration (T-N) of 7 to 10 mg/L in a stable manner.

Example 3-3

In this Example using treatment equipment 240 of FIG. 15, an ammoniumcontaining liquid was treated with entrapping immobilization pellets 216in the same manner as in Example 3-1.

(Test Conditions for Treatment Equipment)

-   -   Ammonium containing liquid: Industrial wastewater having an        ammonium nitrogen (NH₄—N) concentration of 90 to 120 mg/L and a        BOD concentration of 190 to 230 mg/L

Retention time in nitrification tank 212: 6 hours

Nitrification tank 212 packed with contact filter media

Retention time in denitrification tank 226: 3 hours

Denitrification tank 226 packed with contact filter media 28(denitrifying bacteria attached to be immobilized)

Retention time in anaerobic ammonium oxidation tanks 214: 2 hours

Packing ratio of entrapping immobilization pellets 216 in anaerobicammonium oxidation tank 214: 20%

Mechanical stirring in the anaerobic ammonium oxidation tank 214 causeda flow of entrapping immobilization pellets 216, 216 . . . .

After continuous treatment under the above-described conditions andacclimatization for one month, ammonium and nitrite were simultaneouslyremoved, and the treated liquid was maintained to have a total nitrogenconcentration (T-N) of 14 to 20 mg/L and a BOD concentration of 20 mg/Lor less in a stable manner.

When the denitrification tank 226 was not equipped in the treatmentequipment 240, anaerobic ammonium oxidizing bacteria were inhibited bythe BOD component, and the total nitrogen concentration (T-N) in thetreated water was reduced to 40 to 80 mg/L.

Example 3-4

In this Example using treatment equipment 250 of FIG. 16, an ammoniumcontaining liquid was treated with entrapping immobilization pellets 216in the same manner as in Example 3-1. The specification of anitrification tank 212, a denitrification tank 226, and an anaerobicammonium oxidation tank 214 and the wastewater used were the same as inExample 3-3.

The equipment was operated at a nitrified liquid feedback ratio of 100%(50% to the denitrification tank 226, and 50% to the anaerobic ammoniumoxidation tank 214).

After continuous treatment under the above-described conditions andacclimatization for one month, ammonium and nitrite were simultaneouslyremoved, and the treated liquid was maintained to have a total nitrogenconcentration (T-N) of 7 to 12 mg/L and a BOD concentration of 20 mg/Lor less in a stable manner.

Example 3-5

In this Example using treatment equipment 260 of FIG. 17, an ammoniumcontaining liquid was treated under the same conditions as in Example3-1, except for using wastewater not containing BOD and having anammonium nitrogen (NH₄—N) concentration of 90 to 120 mg/L. The treatmentequipment 260 comprises the equipment of Example 3-1 and a molassesaddition unit 242.

When molasses was introduced into nitrate produced in a nitrificationtank 212 to attain a C/NO₃—N ratio of 1.8 to the anaerobic ammoniumoxidation tank 214, continuous treatment was carried out in a stablemanner, and the treated liquid was maintained to have a total nitrogenconcentration (T-N) of 10 to 20 mg/L.

Example 3-6

In this Example using treatment equipment 270 of FIG. 18, an ammoniumcontaining liquid was treated with entrapping immobilization pellets 216in the same manner as in Example 3-1. Multiple nitrification tanks 212were provided (three tanks in this Example), since a high-concentrationammonium containing liquid was used as described in the following testconditions.

(Test Conditions for Treatment Equipment)

Ammonium containing liquid: Industrial wastewater having an ammoniumnitrogen (NH₄—N) concentration of 590 to 820 mg/L and a BODconcentration of 100 to 230 mg/L

Retention time in nitrification tanks 212: 12 hours (retention time ineach tank 4 hours)

Packing ratio of entrapping immobilization nitrified sludge pellets 215in nitrification tanks 212: 20%

Retention time in anaerobic ammonium oxidation tanks 214: 12 hoursPacking ratio of entrapping immobilization pellets 216 in anaerobicammonium oxidation tank 214: 20%

Molasses introduced into anaerobic ammonium oxidation tank 214 at aC/NO₃—N ratio of 0.5

Mechanical stirring in the anaerobic ammonium oxidation tank 214 causeda flow of entrapping immobilization pellets 216, 216 . . . .

After continuous treatment under the above-described conditions andacclimatization for one month, ammonium and nitrite were simultaneouslyremoved, and the treated liquid was maintained to have a total nitrogenconcentration (T-N) of 34 to 40 mg/L in a stable manner.

In Comparative Example, when the equipment was operated with a singlenitrification tank 212 for a retention time of 12 hours, nitrificationdid not proceed, and the treated liquid was maintained to have a totalnitrogen concentration (T-N) of 184 to 540 mg/L. In a conventionaltreatment process with activated sludge, it is necessary to dilutewastewater three times and extend the retention time to two days ormore.

Example 3-7

In this Example using treatment equipment 280 of FIG. 19, an ammoniumcontaining liquid was treated with entrapping immobilization pellets 216in the same manner as in Example 3-1. Multiple nitrification tanks 212and anaerobic ammonium oxidation tanks 214 were provided (three tanks inthis Example, respectively), since a high-concentration ammoniumcontaining liquid was used as described in the following testconditions.

(Test Conditions for Treatment Equipment)

Ammonium containing liquid: Industrial wastewater having an ammoniumnitrogen (NH₄—N) concentration of 590 to 820 mg/L and a BODconcentration of 100 to 230 mg/L

Retention time in nitrification tanks 212: 12 hours (retention time ineach tank 4 hours)

Packing ratio of entrapping immobilization nitrified sludge pellets 215in nitrification tanks 212: 20%

Retention time in anaerobic ammonium oxidation tanks 214: 12 hours(retention time in each tank 4 hours)

Packing ratio of entrapping immobilization pellets 216 in anaerobicammonium oxidation tanks 214: 20% Molasses introduced into anaerobicammonium oxidation tanks 214 at a C/NO₃—N ratio of 0.5 Mechanicalstirring in the anaerobic ammonium oxidation tanks 214 caused a flow ofentrapping immobilization pellets 214, 214 . . . .

After continuous treatment under the above-described conditions andacclimatization for one month, ammonium and nitrite were simultaneouslyremoved, and the treated liquid was maintained to have a total nitrogenconcentration (T-N) of 14 to 20 mg/L in a stable manner.

In Comparative Example for this Example, when the equipment was operatedwith a single nitrification tank 212 for a retention time of 12 hours,nitrification did not proceed, and the treated liquid was maintained tohave a total nitrogen concentration (T-N) of 284 to 630 mg/L. In aconventional treatment process with activated sludge, it is necessary todilute wastewater three times and extend the retention time to two daysor more.

In a conventional process, ammonium treatment essentially involvesnitrification reaction and denitrification reaction. Treatments ofExamples 3-1 to 3-5 using a conventional process require a nitrificationtank retention time of 12 hours and a denitrification tank of 12 hoursto obtain the same water quality. The treatments also require an organicsubstance such as molasses or methanol in an amount three times of anamount of nitrogen, and large-scale treatment equipment. In contrast,when the present invention is employed, ammonium can be anaerobicallydenitrified for a short retention time, and treatment equipment can bemuch inexpensive than in a conventional process.

As described above, when the present invention is employed, a processand equipment for treating an ammonium containing liquid can be providedwhich can denitrify ammonium in an ammonium containing liquid at a highspeed.

1. Equipment for treating an ammonium containing liquid bydenitrification treatment of an ammonium containing liquid containing atleast ammonium, the equipment comprising: a nitrate reduction tankcarried out nitrate reduction treatment of reducing nitrate to nitrite,wherein the nitrate is contained in or added to the ammonium containingliquid, and an anaerobic ammonium oxidation tank carried out ananaerobic ammonium oxidation treatment of simultaneously anaerobicallydenitrifying nitrite and ammonium, wherein the nitrate is produced inthe nitrate reduction treatment and the ammonium is contained in theammonium containing liquid.
 2. The equipment for treating an ammoniumcontaining liquid according to claim 1, wherein the nitrate reductiontank has a structure of bringing the ammonium containing liquid intocontact with pellets in which the heterotrophic denitrifying bacteriaare entrapped to be immobilized, and the anaerobic ammonium oxidationtank has a structure of bringing the ammonium containing liquid treatedin the nitrate reduction tank into contact with pellets in which theanaerobic ammonium oxidizing bacteria are entrapped to be immobilized.3. The equipment for treating an ammonium containing liquid according toclaim 1, wherein the nitrate reduction tank has a structure of bringingthe ammonium containing liquid into contact with pellets to which theheterotrophic denitrifying bacteria are attached to be immobilized, andthe anaerobic ammonium oxidation tank has a structure of bringing theammonium containing liquid treated in the nitrate reduction tank intocontact with pellets to which the anaerobic ammonium oxidizing bacteriaare attached to be immobilized.
 4. The equipment for treating anammonium containing liquid according to claim 1, wherein the nitratereduction tank and the anaerobic ammonium oxidation tank have a cellamount ratio control device of controlling the number of cells of theheterotrophic denitrifying bacteria to 10 to 1,000 times the number ofcells of the anaerobic ammonium oxidizing bacteria.
 5. The equipment fortreating an ammonium containing liquid according to claim 1, wherein thenitrate reduction tank and the anaerobic ammonium oxidation tank have aC/NO₃—N ratio control device of controlling the C/NO₃—N ratio of theconcentration C of the organic carbon contained in or added to theammonium containing liquid to the concentration NO₃—N of nitratenitrogen contained in or added to the ammonium containing liquid to 0.5to 2.5.
 6. The equipment for treating an ammonium containing liquidaccording to claim 1, wherein the nitrate reduction and the anaerobicammonium oxidation are carried out in one anaerobic tank.
 7. Theequipment for treating an ammonium containing liquid according to claim6, wherein the anaerobic tank has a structure of bringing the ammoniumcontaining liquid into contact with pellets in which the heterotrophicdenitrifying bacteria are entrapped to be immobilized and pellets inwhich the anaerobic ammonium oxidizing bacteria are entrapped to beimmobilized.
 8. The equipment for treating an ammonium containing liquidaccording to claim 6, wherein the anaerobic tank has a structure ofbringing the ammonium containing liquid into contact with pellets inwhich the heterotrophic denitrifying bacteria and the anaerobic ammoniumoxidizing bacteria are entrapped to be immobilized.
 9. The equipment fortreating an ammonium containing liquid according to claim 6, wherein theanaerobic tank has a structure of bringing the ammonium containingliquid into contact with pellets to which the heterotrophic denitrifyingbacteria that reduce the nitrate to nitrite are attached to beimmobilized and pellets to which the anaerobic ammonium oxidizingbacteria are attached to be immobilized.
 10. The equipment for treatingan ammonium containing liquid according to claim 6, wherein theanaerobic tank has a structure of bringing the ammonium containingliquid into contact with pellets to which the heterotrophic denitrifyingbacteria and the anaerobic ammonium oxidizing bacteria are attached tobe immobilized.
 11. The equipment for treating an ammonium containingliquid according to claim 6, wherein the anaerobic tank has a cellamount ratio control device of controlling the number of cells of theheterotrophic denitrifying bacteria to 10 to 1,000 times the number ofcells of the anaerobic ammonium oxidizing bacteria.
 12. The equipmentfor treating an ammonium containing liquid according to claim 6, whereinthe anaerobic tank has a C/NO₃—N ratio control device of controlling theC/NO₃—N ratio of the concentration C of the organic carbon contained inor added to the ammonium containing liquid to the concentration NO₃—N ofnitrate nitrogen contained in or added to the ammonium containing liquidto 0.5 to 2.5.